Well they shouldn’t sign a 1b. But Devers and Casas are both among the worst at their positions.
Chapman will unfortunately require a larger deal than the Sox should spend upgrading the infield. After him the best defensive 3b on the market is probably Isiah Kiner-Falefa, who should only be signed as a bench player.
They probably simply go with Urias, who does have some right-handed pop at 2b. Whether they offer arbitration or non-tender him and try to re-sign him for less remains to be seen…