One thing I'm confused about. If I gave my friend my account details for her switch to play my games, could I play say, cities Skylines while she played final fantasy? Or would her game pause if I started playing any game on my own switch?

Cool feature but too bad there's no one I trust to use it with.

Sounds cool and while at first it looks like you could only be playing a game on one switch at a time, keep in mind your primary console doesn't need to be online, fire up breath of the wild in airplane mode on primary switch and someone else could use your account to be playing rocket league online for example

If it is like PS4, then your friend could play your game on her console with your account, while you play on your primary console with another account. As soon as you tried to log onto your account, it would kick her offline, and out of the game.

It is not really game sharing, it is a system to allow you to play your games anywhere. You have to give your account info to your friend and stay off your account while they play.

This is just account sharing not digital game sharing. The end results could be similar but with limitations.

It's a shame they didn't apply game sharing between the family accounts:
"Within a family, members do not share MyNintendo points, eShop account balances, and purchase history."

Either way I guess I could try it out with my family account whenever I set it up.

It's stated in the OP: if the primary console starts playing a game, the person with the non-primary console will have to stop.
But here are some pretty pictures

^Thankyou for sharing that! Probably will never use it

Nice.