So I'm a Spider, So What - "So I'm a spider so what version"

This is very accurate.
Kumoko is one of the rare examples of an OP isekai protagonist that doesn't start the series OP, another example being slime-bro Rimuru. While they start out incredibly strong, for a good while there are still plenty of enemies that outclass them and could squash them like bugs (almost literally in Kumoko's case).
It takes what is going to be effectively the entire first season of the anime for her to get anywhere near OP, and even then it'll probably take until a potential second season before we see the point when she truly becomes OP, since she's still going to be completely outclassed by the genuine gods for quite a while.

Haven't read Slime's LN, but from the anime: He seems pretty strong right from the beginning.