That's actually a very deep question. There's pros who have surfed jaws on wavestorms, and a great video where a pro surfs random shit including a coffee table. So it's not such an easy answer.

We know it's not the board here, as the one you are failing with is meant for bigger and steeper waves. You're doing better on the groveller because it's what you have more experience on.

Seems to be common for beginners to get competent on one board and then struggle when trying a new board. All part of the learning experience.

Now there is such thing as oversizing a board, but that doesn't seem to be the main factor from what you described.