Is it part of the Sunnah to typically write the marriage contract two or three days before the wedding banquet and consummation with the wife? And how should the wedding banquet be according to the Sunnah in detail?

The time for the walimah begins with the marriage contract (aqd). It is preferable to hold it after consummation, in emulation of the Prophet, peace and blessings be upon him, though there is flexibility in the matter. Its time begins with the contract, and it is preferable to hold it immediately after consummation for the sake of emulation. It is not forfeited by divorce, death, or the passage of time.