Some fuzzy thoughts (with some edits):
There are so many different transmission types/variations so I’m not going to even try and get my head around and compare. However, the key point here (I believe) is whether the tractor maintains PTO output at the right speed (subject to engine revs of course) no matter what one does to that bit of the transmission that drives the wheels.
Some geared tractors enable the above with a dual clutch: press clutch pedal only so far to change gear or stop/move forward – press pedal fully to disengage the PTO as well.
Otherwise, it might be referred to as a “live” or fully independent PTO which keeps turning no matter what one does with the clutch pedal/controller for drive to the wheels.
And then, otherwise, it might be a semi-independent PTO drive or a direct drive PTO.
I suspect the best practice for any PTO driven work is a rolling start no matter what the transmission: i.e. get the tractor moving, then bring engine revs up to speed for desired PTO output and (if not already engaged) engage the PTO drive while also lowering the implement (if you can do that at same time!). Of course this means a certain distance of travel that has not been cut (or rotovated or whatever), but that can potentially be done on the next pass. However, field corners or other fiddly bits can be a bit awkward if one doesn't have a live PTO (or, 2nd best, a dual clutch).
Scenario 1 (dual clutch and/or independent PTO): you’ve backed up the topper tight into the field corner; you spin-up the topper while stationary and start cutting and only then slowly engage drive to the wheels (slowly because engine likely to be at high revs for PTO speed unless you have some sort of eco-PTO drive arrangement - of course, there won't be clutch wear to worry about if it's hydrostatic.
Scenario 2 (semi-independent PTO – like mine, which is geared): you’ve backed up the topper tight into the field corner; you spin-up the topper with the PTO clutch hand-lever while tractor stationary and then want to engage drive to the wheels – press clutch (in my case) to engage forward gear and PTO drive is lost momentarily. I have done this, but I try and avoid because it must surely put extra load/wear on the main clutch (especially bearing in mind that engine is at high revs for correct PTO speed). Semi-independent PTO is really designed to allow PTO driven machinery to be disengaged and raised while manoeuvring at, say, the end of a run.
Scenario 3 (direct drive PTO): = PTO only turns when drive to wheels is engaged as well. Forget about cutting the corners/tight spots !!
Alternatively, "one-wheel" braking could potentially sharped up the corner-cut a tad on a running pass without the faff. I've seen some pretty sharp tractor one-wheel braking turns on Youtube, but can't recall whether ever on a 4WD tractor !
In summary, having a live/fully independent PTO drive is the bees knees (increasingly common on newer machines I suspect). Dual clutch would be 2nd best I would say. Otherwise, forget about trying to cut tight corners and tricky bits with the topper unless one-wheel braking can turn your tractor on a button.
Final throw-away thoughts:
Not sure how relevant this will be with tech/engineering moving on apace, but I recall advice that hydrostatic is great for yard work, but that geared transmission is better for field work. I don't know, but a similarly powered engine will produce less Horse Power at the PTO with a hydrostatic transmission than with a geared transmission. I can't imagine that will be an issue for routine pasture topping with a small compact topper though.
This is NOT a recommendation, but if I could afford a newish automatic transmission (hydrostatic or otherwise), I reckon, this far on, that's what I'd probably go for with or without a live PTO.