The main thing missing from #restic's compression feature¹ is what #BorgBackup calls "auto": try compressing a small part of the file to see if it makes sense at all (i.e. if the file is compressible), and skip compressing that file if it doesn't. Right now, restic can only compress all files during a run, or none.
¹ other than documentation; it's not cool that I had to dig through the source to find the difference between "auto" and "max" compression, and which algorithm it's using at all