I run an old gt86, gr86 is effectively a facelift with a bigger engine, so practicalities are the same.
Back seats are good but legroom is an issue if the front seat occupant is tall. I’m 6’2 my wife is 6′ and we can get our kids (5 and 3) in too but it’s a bit of a squish. As a 1+2 (kids behind each other) there’s plenty of space. It’d probably be easier with kids who didn’t need a booster as their feet can go under the seat in front.
Large, long low slack trail bike can go in with just the front wheel off but it’s a bit of a faff, easier with both wheels or a pedal off. 8′ surfboard goes in fine.
Lovely to drive, slides around, fast enough for me. I used to have an mx5 and after that a 944s2, I think it’s the best of all of them. I won’t be buying a gr86 but only because I don’t have the £23k to upgrade. A 10 year warranty makes it a great shout.
The gt86 has a bit of a dead spot in its torque between 3 and 5k rpm, so it feels a bit lifeless in semi-spirited driving. Mooching around or ragging it’s fine, it just means it’s 2nd gear for getting out of b road corners instead of 3rd. Fortunately the gearbox is a peach. The gr86 has a smaller deadspot but also 20% more torque throughout so I imagine it feels more responsive. Superchargers are available if you want