I am up-to-date as of about a day ago with 64Bit Raspberry Pi OS.
I have noticed that I used to be able to go to the guiding tab (which has been rearranged significantly) and I can no longer connect or disconnect and start the guiding because the buttons are deactivated and greyed out. I need to go to PHD2 to do this and this is working fine. Is this a deliberate change of functionality?
Another thing I have found is the manual buttons to control the mount are producing random movements. I found this when I tried to centre the Moon and could not because the movement I either went too far or moved in the opposite direction.
Another thing is that the applications are now using significantly more RAM. I am finding that immediately after starting about 1.3GB is used (which is still a lot) but the next morning it is around 1.7GB.
I have found that if I add the guide camera to the profile the buttons are now active.
This seems to be a bug, as it is not necessary for anything else. The camera is not available for selection, and it does not need to be.I suspect that I could add any camera and it would work, because the camera is controlled by PHD2.
I have not tested it, because it is now daylight and I don't expect clear skies for a week or so.
I am still interested in some answers to the other questions