I carry the saw on my back often. I put shoulder straps on the existing saw case to make a backpack of it. That works when I can shortcut the trail to get to the problem area in the shortest distance. Loop trails are easy to shortcut. Linear trails can be a long distance to walk though. That’s why I mounted the chainsaw to the fatbike.
Do it. I have found the easier I make it to do trail maintenance the less WORK it is. And, the more inclined I am to do it. I have a lot of fun riding the fatty with the chainsaw. I do not enjoying carrying it by hand.
There are stanfard rack mounts built into the seat stays. For bikes without mounts, the same setup can be achieved with a rack designed to mount to the axle. Actually, the rack I used was intended to mount that way. It came with a long scewer. I originally started with a rack designed for fatbikes with built-in mounts. I found that a standard rack meant for a skinny bike worked better in my particular case.