All of these are used to talk about what other people do. Irassharu is specific to being but if someone else is “being” doing something (te iru situation) then suddenly it’s in the mix. It feels like the only time I ever get these right is when I’ve memorized the sentence/answer combo.
I’ve read through the grammar explanations but unless there’s something my brain just skipped over (possible) I can’t see any way to tell which one to use.
Honestly, I didn’t understand it from using Bunpro alone (might have been with the old explanations). It wasn’t until I read chapters 18 & 19 in Genki 2 that it made sense. Additionally I’m using a Genki Kitsun deck that has reviews like ‘honorific version of いる’ and ‘humble version of する’ that my brain slowly absorbed it.
Find some other resources to review until it clicks. I often find that with similar grammar points よう and みたい being the most recent - there will be videos on youTube that compare them - there’s a cottage industry in JLPT grammar videos. You’ll soon find one that makes sense to you. At the moment I find that the https://www.youtube.com/@japanesefromzero often resonate with me.
Could be that some places explain it better than others, more likely it’s the fact that I’m digging around and researching the same grammar point. With new grammar, it’s often vague and cloudy, and then slowly slowly the clouds disspate and understanding is bestowed on me. (Then 2 weeks later the clouds return, lol).
Come to think of it, a lot of that keigo and humble speech grammar points (at the time) were at the end of N4, and I was definitely rushing it to get my N4 complete badge.
Sometimes you’ve got to slow down and understand the concept, otherwise you’ll just end up rote learning the reviews. Been there!