You will likely notice remove unused CSS rules, this is a warning because the extra CSS rules are loading on a page even when they are not needed. You won’t be able to remove all of them because it would be extremely complex to do something such as that and you would likely need to build a theme from scratch with a unique CSS file for each page/widget and then combine them. However, you can remove a decent chunk of these through the use of conditional loading.
Conditionally Loading bbPress
Conditionally Loading BuddyPress
BuddyPress while important for running a community loads a ton of junk on every page load that you can really begin to slow your website down. With a quick edit your functions.php they can all be hidden from everyone else.
As you can see its fairly easy to reduce the amount of scripts on every load and while combining all the scripts as efficient you really want to squeeze out all the performance you can by using these tips with a plugin like Autoptimize. If you have any questions feel free to ask us here or go to our support forums and we can address them!