@robert your post got me thinking. WP-Super Cache (Automattic) uses for sure clean_post_cache() so i did some tests.
Seems to work and update things. Not 100% sure if it updates everything, i will test more and update here. I have left the wpForo cache enable except the HTML cache.
I may have to tinker with this a bit too. I'm pretty happy with my GTMetrix results, but I'm sure they could be improved. I've spent a lot of time trying to make the site as clean as possible to help with load times, and I've been rewarded greatly for that... I went from 8-second load times to 4.4-second load times and the only caching installed on the site is that included with wpForo. I'm also using CloudFlare with some of the advanced caching and minifying tools activated and the host itself has some sort of caching in place. But if WP Rocket gets me to 3 seconds or less, it's probably worth it. Thanks for the info and discussion!