Purchase v-bucks on the phone then have them transfer to the switch once they are bought

yes, you can link your accounts. In order to do that, you have to go to epicgames.com with a PC*, sign in, go to "account", then "CONNECTED ACCOUNTS", and then link it from there.NOTE: there is a small possibility that you will lose your progress, so I suggest that you link it with a test account first

You can use your Epic Games Account to sign in for console. I have a Epic Games acount that I play both on console and PC. So you will be able to use both.

I have done this before on console and I used my Epic Games Account from PC.

Edit: You cant play on both PC and console AT THE SAME TIME. You will be logged out of one. But you can play separatly and go back to playing on PC when your done on console (Example, I play now on PC and on Vacation on Console)

Remiender If you sign in on someone elses console, sign out after use or they might be able to use your account.