From what ive gathered at least on JS’s end, there isnt much enabled as far as caching goes when it comes to TMI nor Twitch-js libraries. As you stated, it may very well be that bigger bots just like mine have private repos which handles their caching, though i havent spotted many(if any) library that provides a cache for developers to attach to. This, also, im bringing from a library in discord. Though both are different platforms, both use IRC. More info can be found HERE