Summary
Williams has had a bit of an up-and-down career thus far. In '18-'19, he came out of nowhere and even started 29 games for the Pelicans. He shot decently from outside and his defense and rebounding numbers were very good. However, those numbers dipped across the board in the '19-'20 season, where Williams missed a chuck of games due to a back injury and saw his minutes decline when he was available.

However, Williams played well for the Thunder this past season, especially during the early parts of the season when the Thunder were actually competitive. He's a career 35% shooter from three, which is decent, and generally just makes the right play on both ends of the court. There's not a ton of upside, and Williams is already 26, but I think he can add value to a good team during the regular season.

I wouldn't expect Williams to be waived, since I think he's a positive value with his minimum contract, but the Thunder may just want to go younger and might not be able to get anything of value for him in a trade. If he is waived, I think teams should seriously consider claiming Williams off waivers rather than letting him hit free agency.
 
Cap Considerations
Williams's $1.8 million salary for 2021-2022 is non-guaranteed, and if he is waived he will become an unrestricted free agent and the Thunder will have no form of Bird rights on him. If he is waived, teams could claim him off waivers, but would need to fit his salary within cap space or an exception to do so, as his contract doesn't fit within the minimum salary exception as it was a three-year contract in order to facilitate the sign-and-trade for Steven Adams.

If Williams becomes a free agent, other teams will have multiple ways to sign him as even teams without cap space could possibly use either of the Non-Taxpayer MLE, Taxpayer MLE, or possibly even the Room MLE to sign him. It's likely that Williams ends up settling for the minimum.