1) Zoom. Players roll for themselves, I roll the DM stuff and run the tables, which is how it's always been. I have a 2nd webcam set up that gives a view of a melee board and figures, so everyone can see that during battles. Whiteboard is very useful, too.
A couple of players are very tech-limited, so we opted not to use Roll20 or OwlbearRodeo
2) Sound and focus. We have an older player who does not hear over any background noise well, and we actually use the transcription option on Zoom to give her a live-feed. It doesn't like fantasy names, though.
Some players do multitask during play, making it a bit slower at times.
3) Every other week, 3 hours.
4) We brought in remote players who couldn't play otherwise. Plus the obvious reduced exposure to health risks. I can also message specific players with info more discretely, which is rare but can be really important. I can drink beer while we play, couldn't do that at our old game shop.
5) Focus and seeing each other face-to-face. Interparty dynamic is a bit broken up.
6) Not really. Closest thing is that for full-party perception rolls, I have to call names one at a time so that I can hear them all.