Not really, from my experience its very easy to share files to apps within shelter, and there are configurable options to make it easier or harder as you prefer.

I know it's going to sound funny, but I, personally, *want* it to be annoying. If it's comfortable, I might do it way more.

Not exactly a solution to your problem, but it works.

For links, you can use UntrackMe, then switch between the accounts. UntrackMe real purpose is to redirect you to websites' FOSS frontends (YouTube to Invidious, Reddit to Teddit, Twitter to Nitter, etc.).

There is probably better app for this, if you don't like the redirects. But if you're going the way of Shelter/Insular, it's a good practice.

For files, if you have rooted phone, you can use Material Files.

If not, you can move files with Files by Google.