First of all fail2ban is not needed if u use csf+lfd, but ... lfd needs a lot of work to filter as much as fail2ban does.
For example Roundcude... very often a target for hackers/kiddies and not dealth with by LFD
So yes.. its a good idea to use fail2ban for things that LFD does not cover. or configure LFD to cover those via regex-custom.pm
Im developing a toll to automate this as its very gard, where for fail2ban its rather easy
Then @Media Schmiede
U are safe, it does not matter that u use a changing ip address.