"Other" storage- offload unused apps

2 questions:

How can I stop "other" storage from filling up? I have a 64gb iPhone SE, and about 3-4 months ago got the notification that my storage was full. I was carrying around a lot of music (40-50GB), so I deleted almost half of that to bring it down to 20G, which gave me plenty of space so I figured I was free and clear. But now I'm again getting the notification that my storage is filling up, and "other" is the BIGGEST storage user (almost 25GB). Why did all my extra space just get sucked up by this category? According to apple I basically have to wipe and restore my phone to get that space back, but what can I do to avoid losing it again? There's no point to creating extra storage if its just gonna keep getting wiped out by this category I have no control over.

Also my phone appears to have automatically started offloading unused apps. This is a setting I've always disabled cause its just annoying pulling up an app I want to use and having to reinstall it. But now my phone just started doing it on its own, I'm guessing in response to the storage. But now I can't find the setting to turn it off, its not even an option in the "recommended" area of storage on my phone where I usually find it, and searching for it doesn't get me anywhere.