Always have at least 3 copies of any important data. Follow the 3-2-1 rule.

Data loss can happen due to so many reasons, the only safe option is reliable and tested backups.

ext4 and others too.

You can ignore the RAM usage, it’s just cache. It uses up to half your RAM by default but if other things need it zfs will just clear RAM for that to happen.

Haven’t seen a single bit of toxic stuff yet, my feed is all cute art and photography.

You can just change the port directly on the application for one of them.