Welcome to the forum.
1: Most dashcams you can get a hard wire kit for, most often sold separate, all Street guardians cameras you can hard wire with what is provided, in their case you just snip off 12 V power plug that you would normally stick into the lighter socket in the dash or center console.
That way however is only for neatness / having your dash socket free for other stuff, it do not support parking guard, to do that with a SG camera you also need a hard wire kit ( aside for the SG9663DR that do come with the hard wire kit due to the nature of that model ( it being a dual remote camera )
In almost all cases you will have a low voltage protection in the hard wire kit, this most often have 4 select able cut off voltages between 11.8 and 12.4 volts ( 12.2 being the recommended one to use )
2: Most cameras are around that FOV, many claim more but that is just BS.
3: Front 1440p do narrow down the options, but there are a few dual systems with that.
4: Yes no dual 1440p cameras yet, i would like to see that though, so rear cameras are most often 1080p
5: GPS are almost the norm to find included today.
6: That narrow it f´down even more to less than a handful of brands like Blackvue - Thinkware
7: Parking mode in a hot place is a tough call with any camera, not least if the car is facing the sun and the camera get direct sun exposure ( you do not want to use one of those sun blocking things to put in the windscreen, a dashcam sandwiched between than and the windscreen risk literally melting.
Otherwise normal operation is fine, also if you have just been parked 4 hours in death valley while you have been exploring the place on foot
8: thats another problem,,,,,, well for some of us at least. buffered mode mean you are relying on a trigger, this could be motion ( extremely rare that work without creating too many false events )
Then you have G - sensor, which do stand a better chance indeed, but this do not mean some punke keying the side of your car get recorded, as that deed are not really a G event per say, a small parking lor door ding might also not be picked up.
Then there is the buffered part, and that do also work if the trigger was there, but in worst cases you have a few seconds from before,,,,,,, which could also be just fine.
Personally as a new comer to parking mode i prefer the always recording low bitrate, paired with G sensor if there is a actual big event.
But ! even this have some downsides to it.
It might be something small the G sensor dont trigger by, and even if you sit and look / listen to every second of parking mode you record the door ding might not be recorded by the MIC.
And there is a chance you yourself probably dont notice a little door ding, not least if it is not on the driver side of the car.
Another downside of always record low bitrate is that the files are considered as regular files, so they are not locked as is, that would only happen if a trigger get kicked off.
So on my view if you are going to be using parking guard it is imperative to pair that with a substantial sized memory card that at least allow you a day or two of buffer before a event might get overwritten.
Personally i dont feel like a need for parking guard, but when brands send me a camera that can do that and the hardware to do it, then i must of course do it, but then i generally do it on a timer or at least with a very high cut off voltage to save the little battery in my little car.
At home i have CCTV on my car as thats a much better option there. ( i live in a 2 floor apartment my IP camera are screwed to my balcony door filming my car parked in the back yard )
If i was to use a smart system, i would be extremely miffed if i got notifications too often on my phone,,,,, not least since i am a avid phone hater but still have one for other reasons ( old sick mother )
My IP camera at home have smart motion detect, it only set off if something human or vehicle shaped get within 1 M of my car, so i can sleep without getting woken up by notifications on my tablet on my bedside table.
