Guys at Unity Technologies were pretty active the last month. A lot of how-to pages were added. I haven't found any new advice there, but it's convenient to have them all compiled in one place.
The how-to on the project setup mentions:
Switch to IL2CPP
Switching the scripting backend from Mono to IL2CPP (Intermediate Language to C++) can provide overall better runtime performance. However, it can also increase build times. Some developers prefer to use Mono locally for faster iteration, then switch to IL2CPP for build machines and/or release candidates. Refer to the Optimizing IL2CPP build times documentation for more on reducing your build times.
I haven't compared mono to il2cpp performance in my games, but I have seen forum posts where devs shared that mono is faster for them. Have you measured your games? Was it true for you?
https://discussions.unity.com/t/in-case-you-missed-it-august-2025/1681933