Is it possible to disable the notifications that you get after triggering an action on the companion app? EG: I don’t need to know that my office AC was successfully turned on via the notification dialog since I’m sitting right under it 
This is a security feature from apple. So no, what I do to solve this is use HA API to get the things done, works without the extra popup
There are plenty of guides around. Simple search on this forum will help a lot!
Edit it in the notification settings of your iphone.