lcalamar SIGNAL-- Any pros/cons of replacing the messaging app w/Signal? (Haven't used Signal on a phone for quite a while - I can still use it for sending texts to non-signal users? (non-encrypted)?
Yes you can use Signal for both E2EE Signal Messages and SMS. I do. Just have a heightened awareness of the status of the send button before doing so ;). Also be mindful that when using Signal or any other third party SMS app you will not be able to receive SMS across secondary user profiles. Only the stock messaging app facilitates this use case.
Phone App -- Pros/Cons of using the GOS phone app vs Google Phone App (will likely use it from my work profile)? Will the GOS phone app have the same 'anti-spam' features which Google is very good at?
I do not use the Google Phone App but anything requiring system level privileges like Call Screening won't work as far as I understand.
Camera -- Does it make any sense to use the GOS camera app in my owner profile but have the Google camera app in my work profile? My understanding is the GOS camera app is very very close to the google camera app so maybe this is a moot question?
I use the GOS Camera for my main point and shoot option, just comparing normal Photo mode on each app they trade blow for blow in quality. I keep GCam in my Play Services profile for the occasions where I want to use the other options. However don't forget that GOS Camera has these coded in ready to go via CameraX API but is just waiting on the vendor extensions to be made available on Pixels. If you want to use GCam though you can do so alongside just the GSF (Google Services Framework) with it's permissions revoked.
Syncing photos -- what is the best 'private' way to auto-sync photos to my NextCloud instance? (the nextcloud app isn't very good), I also only want a 1-way push to NextCloud... even perhaps the ability to set it up on a schedule and review what will sync?
Any cloud service provider can be used alongside Cryptomator to ensure security/privacy with your files properly encrypted. However Nextcloud does indeed have it's merits. Case of you pays your money you takes your choice.