Backup guide and options?

First of all, I would like to thank the community for the great support and tips all over the forum and so far I am in love with Unraid. I would also like to point that I am not very techy person but I am good in following tutorials so I had success with setting a media automation which works very well so far. I would like to make manual periodic backups (one per year or when significant changes have been made - new apps, settings, general updates etc.) to external SSD and/or USB flash, which wont be connected to anything once the backup is on it. So, I would appriciate some general tips and points which can help me.

These are the things I want to backup:

1. Unraid settings

2. Docker containers with their individual settings, port mappings etc.

3. Since this unraid is mainly used for media server automation with plex and some arr apps + adguard, I don't need the media files, just the settings of the apps, aka I don't want to backup all the movies, tv series, songs and books that I have downloaded.

4. Got 1 Ubuntu VM with Litespeed server on it which I use for mail server and web server for 3 personal websites - I would very much like to backup these too. I mean I can probably export a backup from each website and skip the VM backup and in case of failure I could just rebuild a new VM and import the sites backups but isn't there a more convinient and faster method?

Some notes:

I have noticed that in My servers dashboard I have an option to "Generate a flash backup". What exactly does it backup? Is it only the Unraid settings without the docker apps settings and the VMs? Also, If I have that flash backup on my Windows PC, how to restore it in case of drive failure?

Also, I am not sure how to restore a generated backup at all, not only the flash backup, so I would appreciate some tips for these too. Assuming I have all the backups on external ssd/usb and I put in my Unraid a completely fresh SSD and USB.