Third Coast Bancshares, Inc.

BY AND AMONG THIRD COAST BANCSHARES, INC., THUNDER MERGER SUB, INC.

AND GREAT PLAINS BANCSHARES, INC. Dated as of October 6, 2026

Merger of Merger Sub with and into Great Plains

Treatment of Deferred Compensation Plans

ARTICLE II THE CLOSING AND THE CLOSING DATE

Time and Place of the Closing and Closing Date

Actions to be Taken at the Closing by Great Plains

Actions to be Taken at the Closing by TCBX

ARTICLE III REPRESENTATIONS AND WARRANTIES OF GREAT PLAINS

Compliance with Laws, Permits and Instruments

Transactions with Certain Persons and Entities

Voting Trust, Voting Agreements or Shareholders' Agreements

Interest Rate Risk Management Instruments

Fair Housing Act, Home Mortgage Disclosure Act, Real Estate Settlement Procedures Act and Equal Credit Opportunity Act

Usury Laws and Other Consumer Compliance Laws

Bank Secrecy Act, Foreign Corrupt Practices Act and U.S.A. Patriot Act

Unfair, Deceptive or Abusive Acts or Practices

Agreements Between Great Plains and its Subsidiaries; Claims

ARTICLE IV REPRESENTATIONS AND WARRANTIES OF TCBX

Compliance with Laws, Permits and Instruments

Registration Statement and Joint Proxy Statement/Prospectus

Directors' and Officers' Indemnification and Insurance

Regulatory Filings; Registration Statement

Conduct of Business in the Ordinary Course

ARTICLE VII CONDITIONS PRECEDENT TO THE OBLIGATIONS OF GREAT PLAINS

ARTICLE VIII CONDITIONS PRECEDENT TO THE OBLIGATIONS OF TCBX AND MERGER SUB

Nonsurvival of Representations, Warranties, Covenants and Agreements

Articles, Sections, Exhibits and Schedules

Exhibit"B"Form of Director Support Agreement

This AGREEMENT AND PLAN OF REORGANIZATION (this "Agreement") is effective as of October 6, 2026, by and among Third Coast Bancshares, Inc. ("TCBX"), a Texas corporation and registered bank holding company under the Bank Holding Company Act of 1956, as amended (the "BHCA"), Thunder Merger Sub, Inc. ("Merger Sub"), an Oklahoma corporation and wholly owned subsidiary of TCBX, and Great Plains Bancshares, Inc. ("Great Plains"), an Oklahoma corporation and registered bank holding company under the BHCA.

RECITALS WHEREAS, TCBX owns all of the common stock of Third Coast Bank, a Texas banking association with its principal office in Humble, Texas ("TCB");

WHEREAS, Great Plains owns all of the common stock of Great Plains National Bank, a national banking association with its principal office in Elk City, Oklahoma (the "Bank"); WHEREAS, the Board of Directors of TCBX (the "TCBX Board") and the Board of Directors of Great Plains (the "Great Plains Board") have determined that it is advisable and in the best interests of their respective companies and their shareholders to consummate the strategic business combination transaction provided for in this Agreement; WHEREAS, on the terms and subject to the conditions set forth in this Agreement, TCBX will acquire Great Plains through the merger of Merger Sub with and into Great Plains (the "Merger"), with Great Plains surviving as a wholly owned subsidiary of TCBX;

WHEREAS, immediately following, and in connection with, the Merger, TCBX will cause Great Plains to be merged with and into TCBX, with TCBX surviving the merger (the "Second Step Merger" and together with the Merger, the "Integrated Mergers"), and immediately following the Second Step Merger, or at such later time as TCBX may determine, TCBX will cause the Bank to be merged with and into TCB, with TCB surviving the merger (the "Bank Merger"); WHEREAS, following the Bank Merger, TCB will use the name "Great Plains Bank, a division of Third Coast Bank" at the former branches of the Bank;

WHEREAS, concurrently with the execution and delivery of this Agreement, as a condition and inducement for TCBX to enter into this Agreement, certain shareholders of Great Plains have each entered into a Voting Agreement in the form attached hereto as Exhibit "A"(the" Voting Agreement "), whereby such shareholders of Great Plains have agreed to vote the shares of Great Plains Stock (as defined below) owned by them in favor of this Agreement, the Merger and the transactions contemplated hereby and thereby;

WHEREAS, concurrently with the execution and delivery of this Agreement, as a condition and inducement for TCBX to enter into this Agreement, each of the directors of Great Plains and the Bank have entered into Director Support Agreements in the form attached hereto as Exhibit "B"(the" Director Support Agreement ") in connection with the Merger;

WHEREAS, concurrently with the execution and delivery of this Agreement, as a condition and inducement for TCBX to enter into this Agreement, the executive officers of Great Plains and/or the Bank set forth on TCBX Confidential Schedule 8.09 have entered into employment agreements with TCBX and/or TCB in connection with the Merger; WHEREAS, it is intended that the Integrated Mergers together will be treated as a single integrated transaction as described in Rev. Rul. 2001-46, 2001-2 C.B. 321, that qualifies as a "reorganization"under Section 368(a) of the Internal Revenue Code of 1986, as amended (the" Code ") and the Treasury Regulations promulgated thereunder, and this Agreement is a "plan of reorganization" within the meaning of Treasury Regulations §§1.368-2(g) and 1.368-3(a) for purposes of Sections 354, 356, 361 and 368 of the Code (and any comparable provision of state Law); and

WHEREAS, the parties hereto desire to set forth certain representations, warranties and covenants made by each to the other as an inducement to the execution and delivery of this Agreement and certain additional agreements related to the transactions contemplated hereby:

AGREEMENT NOW, THEREFORE, for and in consideration of the foregoing and of the mutual representations, warranties, covenants and agreements contained in this Agreement, and other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, and subject to the conditions set forth below, the parties, intending to be legally bound, undertake, promise, covenant and agree with each other as follows:

ARTICLE I THE MERGER Section 1.01 Merger of Merger Sub with and into Great Plains . Subject to the terms and conditions of this Agreement, at the Effective Time, Merger Sub will merge with and into Great Plains in accordance with the provisions of Section 1081 of the Oklahoma General Corporation Act (the "OGCA"). Great Plains will be the surviving corporation in the Merger (the "Surviving Corporation") and will continue its corporate existence under the OGCA. Upon consummation of the Merger, the separate corporate existence of Merger Sub shall terminate.

Section 1.02 Effects of the Merger . The Merger will have the effects set forth in the OGCA. The name of the Surviving Corporation will be "Great Plains Bancshares, Inc." Section 1.03 Certificate of Incorporation and Bylaws . At the Effective Time, the certificate of incorporation and bylaws of Great Plains, as in effect immediately before the Effective Time, will be the certificate of incorporation and bylaws of the Surviving Corporation until thereafter changed or amended as provided by Law. Section 1.04 Directors and Officers . The directors and officers, respectively, of Merger Sub at the Effective Time will become the directors and officers of the Surviving Corporation and will hold office from the Effective Time until their respective successors are duly elected or appointed and qualified in the manner provided in the certificate of incorporation and bylaws of the Surviving Corporation or as otherwise provided by Law.