You can (and should) export & backup your following list.
Migrating posts is complicated -- it's straightforward to export all your posts with third party tools, but you shouldn't expect to be able to move them to a new instance unless you're running it yourself, in order to avoid the possibility of faked histories. (I personally keep a backup of all my posts, and it's fairly straightforward to re-format them as a static html document if you feel like you need to re-host them for archival purposes.)
Personally, I recommend keeping accounts on several instances, and posting to different accounts corresponding to your various interests. This makes it less irritating for members of your social group that don't want to hear about particular topics, makes migration in case of instance apocalypse easier, and encourages you to stretch out your identity a bit (rather than feeling like you need to stay 'on-brand' like people do on twitter).
Migrating posts is complicated -- it's straightforward to export all your posts with third party tools, but you shouldn't expect to be able to move them to a new instance unless you're running it yourself, in order to avoid the possibility of faked histories. (I personally keep a backup of all my posts, and it's fairly straightforward to re-format them as a static html document if you feel like you need to re-host them for archival purposes.)
Personally, I recommend keeping accounts on several instances, and posting to different accounts corresponding to your various interests. This makes it less irritating for members of your social group that don't want to hear about particular topics, makes migration in case of instance apocalypse easier, and encourages you to stretch out your identity a bit (rather than feeling like you need to stay 'on-brand' like people do on twitter).