I can't think of any advantages. Unraid is essentially a clean install each time it boots. If you really want to get rid of all your webUI settings I guess you could start over, but you can just change any you want and keep the rest without starting over.
Are you really planning to remove disks, or just reformat them? If you change disk assignments you have to New Config and rebuild parity, but reformatting is different and parity is maintained during format.
No point in balancing, and if you reload user shares with the default Highwater allocation they won't be balanced anyway. And Highwater is default for a good reason, it is a compromise between using all disks (eventually) without constantly switching disks just because one disk temporarily has more free space. Most Free allocation will be the most balanced in a way, but has other disadvantages that can affect performance and keep disks spunup.
I've never bothered with btrfs in the parity array so maybe someone else will have an opinion.
Depends on your use of course. That would be plenty for dockers and VMs, and some user share caching. Do you cache a lot of user share data every day? I say every day because mover is intended for idle time and daily in the middle of the night is default for good reason.
Latest beta allows multiple pools. I have 2x500G SSD as btrfs raid1 "cache" pool for user share writes, and 256G nvme as "fast" pool for dockers and VMs. Way more than I need but I just happened to have them.