This and part 3 and 4 deal with extra things that make it all better for teachers and students. That is, they don't change the "performance" but they really change the experience. I want to offer what you can do to make on-line teaching or learning a better experience, which leads to less stress, and more comfort at both ends of the connection. We all know that we learn best in a comfortable, stress free, "happy" environment, so it's worth taking into consideration.
So you can do without all these things, but we want distance teaching/learning to be sustainable, and these things have all really gone a long way towards that goal for me and my students.
Headphones - I'm going to likely disagree with many other posts by other people on a similar topic - just my experience.
I was a long time resister of headphones and ear buds - I've never liked the sound; it always seems wrong and artificial. My voice sounds odd with my ears covered, and I can't play properly without hearing the nuances of my harp. But listening to students all day on laptop speakers is not good for the ears and head either.
To the rescue - open back headphones! These are just beautiful, and saved me from going mad teaching all day. Open back headphones are just what you think - instead of your ears being blocked, the backs (the part over your ears) have a grill on them that lets sound in very well. And somehow the sound through them seems to come from the room instead of the middle of your head (not a sensation I like!) They are the polar opposite to sound cancelling headphones and I love them. The ear cup is large and rests on your head around your ears, not on them. Very comfy.
This means you can play, talk and listen, and everything is at its normal volume. The ones I use are Sennheiser 599, but the there are other comparable brands. There are no cheap open-back headphones, just a bit expensive and more expensive. I recommend the corded version with a good long cord, because every bit of latency bugs me.
I see many people recommending mics, but my experience has not been so positive. I have an older Blue snowball USB, and now a fancy Blue Yeti desk mic, and one in each of the webcams. However, what sounds the best to those on the receiving end of the Zoom call has consistently been the mic or array of mics in the laptop. So happily, I don't need one more thing on the table/desk. If I was streaming a larger group, I would use the Blue Yeti, or my Zoom video recorder with its very excellent mics. If you use a newer cellphone it might have an excellent mic. Tablets vary from terrible to fantastic, and older laptops are often terrible, so you need to ask what other folks are hearing. Don't forget to adjust your audio settings, advanced, on Zoom, to eliminate the focus on speech frequencies by disabling the intermittent and continuing background noise options. If speech and instrument sound is not clear to others after attending to the settings, then a USB mic is what is needed.
Small caveat - if you have an external audio processor for your computer (like a Scarlett solo, or one of the many excellent Roland products) you can use a regular 1/4" or XLR jack microphone. If you have those already, no need to buy more, and the sound will be excellent. Better than USB I think.