Zee,
IMHO......
Assetto Corsa is more of a proper racing sim and has an enormous following of modders and skinners.
It is getting on but it just seems to rock on.
Assetto Corsa Competizione gets quite a few kilometres from me, but it is primarily focused on the single GT Series.
Can't really comment on Forza Horizon 5 but based on previous versions I think (just me, myself) it's more 'Gamey' than Sim.
Then again, I still enjoy Project Cars 2.........................
I just think there's a long learning curve here, lots of mods, addons and a lot of question marks - like where to get everything from and how everything works together. I wish there was a site with 'step by step how to get everything running in AC'.
Only thing I don't like is AC only seems to be available through Steam. Steam app is known to run background tasks on your system and uses some valuable computer resources in doing so. I ultimately would like to have MSFS2024 on one dedicated drive, and AC on another dedicated drive. I guess i have some Googling to do, lol !