Collins had 100+ tackles and is only in year 2 with a coach that isn't really known for developing LBs. He'll be fine.
Simmons rated as a "solid" DB according to PFF (
link). I still think of him as a missile without a guidance system. There's no doubt he's made several game changing plays over the past 3 years. The INT in overtime against Seattle in 2020, goal line stop against Trey Lance in 2021, and the forced fumble against the Raiders in 2022 come to mind. That's 3 wins because of Isaiah Simmons.
I would say Isaiah was played out of position. I'd like to see him focused on one position. He looks like a WLB to my eyes, covering RBs, weakside cutbacks, occasional pass rush and occasionally covering a Y in the flat or backup TE.
A new coach will do wonders for both of these guys IMO.