I think you misunderstood, Virtual Game Card is fully digital, new system, to lend diigital games to another switch.
Maybe you’re thinking about Game Key Card? Which is a physical key without game file, so need to download the game itself
You can only set one Switch as primary account.
you can play with your own account in your own switch, while your friend plays in his Switch that is set as your account’s primary. Previously both can play the same game at the same time (I did a while ago to play MH rise with my friend, using one game and one NSO subscription). Seems this is no longer possible after the new update
Yes, we did play online on the same party. In contrast, we can’t play local network party together so need to be Online