>>> If APPM will be able to platesolve using ASTAP directly, and I have an ASCOM camera (which APPM can also use) then no other intermediate software (SGP, NINA, etc.) is needed?
What may be confusing in the prior discussion surrounding NINA, basically it was to allow NINA to control the camera. This allowed the process to run without disconnecting the camera from NINA to connect to APPM (or whatever), and then reconnect to NINA. So handy for NINA users, but not implying NINA was a requirement for ASTAP.
Unlike mounts, cameras can connect to only one application at a time.