I highly recommend the 400. Weight like a 362, power like a strong 440. It's my rear handle saw of choice for climbing. I used it today once the 2511 ran out of bar length. Eventually the 400 even ran out of bar length(25",) and I even took the 500i w/32" aloft.
No timed cuts compared to a 200t. The biggest difference was the responsiveness after porting and bumping up the compression. My 201tcm just revved slowly...advancing the timing isn't really a "thing" on the newer 201s. Just throwing a degree wheel on it, it was apparent why it built revs slowly.
The cylinders are so small, you can't do much with them, but it doesn't take much to wake them up.
Mine sounds pretty good now. I muffler modded it with a piece of tubing that comes out the side. I even put it at a 45* angle so it looks like a hot rod lol. Sorry, but no pictures. I think my favorite sounding climbing saw is my MM'ed 2511t...sounds like a swarm of angry bees. My favorite sounding saw of all, is my triple port 066. Obnoxiously loud, but has a nice deep lope at idle.