I'm conducting remote User testing interviews for 2 years now and these are my learnings and recommendations:

- I would recommend you to build a prototype in any software tool out there like Figma, Sketch, XD or Invision and have them open the link. 
You can build the prototype around the features you want to test and you can share the link at the beginning of the interview. 

- Don't ask them to install any software on their phone.

- I will kindly ask them to turn on their camera during the whole interview, this is something they agreed from the start before even scheduling the interview

- I will let them know they are recorded and ask them if they are ok with that

- If I'm testing mobile designs, I'm asking the participant to open the prototype on the desktop and share their screen but also on their mobile device. I might be asking them to redo some tasks on their mobile device and to let me know if they struggle with something when performing the same task.

- missing out on the non-verbal communication, it's just a myth. I got a lot of that during testing sessions :)