I've been heavily using MuseScore 4 lately and haven't noticed that type of latency on the Linux AppImage. My only gripe with 4 is the inability to open multiple scores in tabs. It opens them in separate windows instead. It makes closing scores in that situation difficult. If you have two open windows and quit one of them, both quit. If you instead just close one of the scores the window remains open with nothing in it. It seems to be a can't/won't fix problem as it has to do with their new soundpack system. It's probably the number one gripe users have with 4.