I'm looking for advice on how to get started with a NAS, probably Synology since it's beginner friendly and often well recommended. I'm thinking of a 2 bay case with 2x4TB HDDs in RAID1 setup. What do I have to look out for in a device to get the best bang for my bucks?

My use case:

I have various documents, software projects, family pictures, videos that I want to store on something more reliable than a bunch of internal/external HDDs or USB sticks. I have a full *arr stack and jellyfin but I want to move these to my "server" laptop and docker once NAS is setup, and then host the files on it. For projects I might want to self-host gitea down the line.

Some more specific questions:

1. if I go with a 2 bay NAS case, can i also connect my old external drive to it as a separate drive, can they handle USB3 drives? Will it require reformatting since it was used on windows so far?
2. are there any issues with connecting docker ~~drives~~ volumes to a NAS?
3. noise issues - does the NAS itself make a noticeable amount of noise or is it just the drives?
4. whats the life expectancy of a NAS? if it dies, can I just plug the drives into a new one?
5. does syncthing work well with a NAS or is there a better way of syncing local files to the NAS for backup?

Sorry for the question dump, just wanted to cover as many possible issues as possible 😅