Any specific apps? I'm not having performance issues on an iPhone SE 3, which should be a lot less powerful, but perhaps I haven't bumped into them. Or maybe apps use different resources on a less powerful phone?

Siri was broken for me for the first few days but suddenly began working again! That was frustrating, but I'm happy it's back. I have no clue what fixed it because it wasn't a software update.

Re: performance, I disabled Apple Intelligence (it’s useless anyways) and noticed a big perf improvement on my 16 plus.