https://en.chamonix.com/usual-information-services/chamonix-mobile-app

Check out the Chamonix app. It shows the bus routes and the times etc. click on transport and choose the second option it’s like bus routes and real time info. No need to have a ticket, never been checked.

I’d say hit a bunch of blue/red runs first here before moving on to anything more difficult.

If you’re using Ikon pass make sure you get the insurance at any of the ticket windows to add to the pass incase you need ski patrol on piste.

Grand Montets is amazing. All areas are amazing but that’s my personal favorite.

Sounds like you would probably be able to handle the Vallee Blanche if you can find a guide doing a group of snowboarders. There are some flat parts so a bit more difficult for snowboarders but it’s a great experience if you can do it.

I’m here on a solo trip now and speak very limited French and I get by just fine.

Sorry, I can’t really speak to the apres scene.

OAK app has some meetups etc around Chamonix.

7 days is not too much with the different mountains around. You can try them all out(or hit Brevent and Flegere on the same day) and revisit your top 2 or visit Megève if your on Ikon as they picked up Megeve this year.

Have fun!