If you want a larger cabin space with enough room for someone to sit comfortably you're going to have to move into a mid-sized or cuv/suv, which is the Passat or larger.
The Jettas, the Golfs, and the A3s are all comparable year to year. If you sit in one, you'll have sat in them all.
My suggestion, for what it's worth, is to scratch your itch for modern convenience with a 2015 TDI. My buddy is 6' 7" and he was going through the same decision and fit luxuriously in a 2015 Passat. He has an English Pointer. I asked him if he was buying the car for the comfort of any potential buddies or family he has to cart around or himself and his dog? I found him a steal on a 2015 Golf and he loves it.
My GSW and his Golf are the same. My Beetle and your Golf are close to the same. My GSW is much more comfortable than the Beetle, but the Beetle is not uncomfortable by any means. My buddy has a tight fit in the Beetle's passenger seat, slid all the way back with his knees kinda up in the door and dash. He fits comfortably in his Golf with the seat all the way back and fully adjusted. The back seats are flat for his dog, but there wouldn't be room for an adult to sit behind him if the seats were upright.
I don't know what you could get for your golf, but it's a desirable model. The 2 door Golf commands the higher end of the ALH market, imo, but the condition of the engine is a significant hit to the value. If you got a couple thousand for it, would it be worth it to sell?
My beetle isn't likely to get me more than a couple thousand and only if I found the right buyer. Whenever I get bored I throw something fun on mine, like nozzles or a turbo. If you have the room I'd suggest turning that Golf into your fun weekend car.