The film leader does need trimming, other techniques like the card insertion or removing the lens are hazards risking shutter damage, and slow, i.e. web techniques & not how it was designed, you need scissors and care to cut the recommended leader, 22 or 23 holes, factory cassettes (or loads) all used to come with the correct leader (before '71 or so). If you fly commercially you will lose swiss arm knives, with little scissors... dont ask... You can get leader templates Leica >>$ or plastic clones.

The only ergonomic problem with a Barnack and many of the early clones is the shutter dial rotates, when the shutter is release and if you are accident prone and snag the dial you get un-even exposure across the frame. You need to be deliberate.

Most lenses will clean up when dismantled, but some will re-fog after a short interval.

The old lenses do give a nice signature with both colour or mono film, (even with d&&&&&&, oops). They do need hoods, more than modern lenses.