I think that after next week I'll join iRacing to see what that's all about. The cost is a little off-putting, but I'm really craving a sim with a well populated online with many different race classes and some good weather simulation and excellent VR.
Whilst sims like AC can be modded, it's a pain. The UI is dreadful (even using CM), and mods can vary in quality massively.
I'm planning on putting up a post tomorrow on how to signup for iRacing and the league, which will include the basics on getting started into the Included content. It'll also include the schedule so we can make sure that it all fits into a 1 month subscription starting on Aug. 1.