So, the Golf/JSW discussion is purely a cargo discussion since the cars are identical from the nose to the back of the back seats. In my opinion, your biggest problem will be from 6-12 months, and really more-so if you have a second child.
Cargo: A stroller and all of the rest of the gear will fit in a Golf for daily use, but you may sacrifice room for other stuff (like suitcases) if you take long trips. I rarely use the entire cargo room in the JSW for everyday stuff, and we have a reasonably large stroller. It'll be useful, though, on our yearly driving vacation, where we need a week+ worth of gear for all of us.
Regarding seating: We definitely have to move the passenger seat forward with the infant car seat in, but it's not too bad now, and it's because we have a full size car seat behind the driver's seat for my 4yo and I can't put the infant seat in the middle. I'm concerned when we have to put a non-carrier (convertible) seat in, but it'll work out until 12mo when she's forward facing.
We had a full-size convertible car seat in rear-facing mode in the old Jetta, which had a smaller back seat, but with the first one you can (and should) put it in the middle and it actually impacts the front seats less. I really do not think it would have worked if I'd had to put it behind the passenger seat, but it's enormous (Britax Marathon).