In my experience it depends significantly on the acoustics of the room. If the room is boomy, it is usually better to elevate the cabs and stand closer to them. Putting the speakers on the floor and standing too far away is not going to help anyone under this circumstance. You will blow out the room, it will sound awful, and you won't be able to hear clearly.
If the room is relatively dry, it may be better to stack the cabs on the floor and vary your distance for the desired balance, but it depends on the tone you want. You can still tilt the top speaker back to aim at your ears. If the drivers are relatively close together and the splay is relatively limited, the sound will integrate nicely. I usually still prefer my speakers elevated.
IMHO there is no one size fits all solution. I suggest considering the acoustics and adjusting as appropriate.
Yes.
I guess the only difference between the two approaches is what you start with (what is the default setting).
I start with my rig placed on the floor. If it sounds good, I leave it that way. If it doesn't, I need to adjust. Sometimes I end up lifting the rig off the floor.
You start with the rig lifted. If it doesn't work in the room, you may end up with the rig placed on the floor, I guess.
It's all about adjusting to the acoustics of the particular room.