Thunderbird mbox vs maildir and switching between them


I use thunderbird sinc its very first version (I switched to it from netscape communicator). I use pop and keep all the messages (in trash) My TB folder is 31GB now.
I have been reading about mbox vs maildir, it seems switching to maildir will do using of TB faster and backups easier but

*Links from mozilla are not updated since 2017.
*I’m not sure if converting folders from mbox to maildir is secure.

What do you think about it?

best regards