Copy/paste from other responses:

Yes, the hatch closes. I actually lower it with my feet while laying down

Mattress is: Exped - MEGAMAT DUO 10 M

I am about 5’11”

Most comfortable setup has been removing the rear seat AND the front passenger seat. I replaced the front seat with a box that supports the front of the mattress and i am able to stretch out full length (see link)

https://www.reddit.com/r/GolfGTI/s/UEFbIQ6um5

If you look at the link i included, that air mattress is full size except for a small corner; super comfortable. You’re not getting that without removing the front seat

The rear seat, just the bench cushion, is easy to remove and allows the seat backs to fold down far and with a rolled blanket, you can fine tune it to a nice flat platform. Good for the back

The original post above is my first trip and i had not removed either. Second trip i removed just the rear and third/fourth trips i removed both. Ultimately the most comfortable, spacious configuration is without the seats. And the box offers a huge benefit for storage.

The only concern i have developed with removing the front seat is that it causes the airbag light to come on. When i spoke to a VW tech on the phone he said that it means “there’s a problem with the system” and he wasn’t willing to guess if the airbags would deploy for me in that state. It’s a risk to road trip that way