As for the Switch and Nintendo Online, I didn't find it confusing or difficult at all to set up a child's account, make sure they can't buy anything without my permission, and then I make sure my daughter knows what she can and can't do, and I keep an eye on it to make sure she follows my rules. I don't trust parental controls to do everything for me.
Now that said, Minecraft on the Switch is one gawd-awful frankenstein amalgamation of permissions and accounts run by Nintendo and Microsoft. I got that working but it's by far the worst experience I've ever dealt with to play a game, even single player.