I have a process to always follow my followers (and unfollow unfollowers) so I can DM them.
Regarding the checks, the initial free plan (just following my bot) comes with weekly checks. That means I'll fetch your followers once a week and compare with last week's, find out who is missing and sending you a DM with the list of all unfollowers. So you'll basically a weekly DM with unfollowers.
Daily, hourly and realtime plans work in the same way but with a higher frequency, but without any kind of digest, just one DM with the list of unfollowers in the time window.
Regarding the checks, the initial free plan (just following my bot) comes with weekly checks. That means I'll fetch your followers once a week and compare with last week's, find out who is missing and sending you a DM with the list of all unfollowers. So you'll basically a weekly DM with unfollowers.
Daily, hourly and realtime plans work in the same way but with a higher frequency, but without any kind of digest, just one DM with the list of unfollowers in the time window.