Thank you for your message.
The issue one is Screen recorder just record a login screen, not the RDP session.
Unfortunately this is expected behavior which occurs due to the fact that Remote Utilities works in a console session, i.e. the Screen record feature always records exactly what is displayed on the remote machine's screen (i.e. login screen in case with an active RDP session).
The issue two is while start View Only on computerA, user will find RDP screen become black screen, once computerA exit View Only, user's RDP screen will return to normal.
Unfortunately, this is expected behavior which occurs due to the fact that the desktop OSs (such as Windows 10) does not allow to simultaneously run a console session and RDP - this is only possible with server OSs if the terminal server is set up (i.e. if there's an active RDP session on the remote machine, connecting to the machine in a Full Control/View Only connection mode will only log out the previous RDP session).
Please note that in case if there are existing terminal sessions running on the remote computer you should be able to switch to the terminal session using an dropdown menu on the Full Control mode toolbar
Hope that helps.