Question about ASUS Prime B450-Plus

Yes, there is an M.2 slot for an SSD, the best SSD, which also lasts the longest because it offers excellent write performance, would be the Seageate FireCuda 530 series, e.g. this variant, which achieves total bytes written values of 2550 terabytes:

Seagate FireCuda 530 (1000 GB, M.2 2280)