Short answer: yes! I have a mustang that I have evented on and off for a few years.
Long answer: they come in every shape and size and flavor under the rainbow. You get way more variety in them than in the average breed, since they are essentially bred by natural selection.
I’ve seen some amazingly successful, talented, athletic, and personable mustangs do very well in just about every discipline. My own mustang could easily have gone through Novice had I had the time/money to pursue that any further.
I’ve also seen some rank, ugly, and downright nasty mustangs.
Bottom line: evaluate the horse in front of you very closely, both in build and in personality. If you’re picking one up straight from the BLM, you should either feel confident in your own knowledge and ability to assess a brand new horse quickly, or bring someone you trust. You should also have a good plan for early training. If you’ve never worked with a tricky horse from the ground up, work with a trainer who specializes in mustangs. They are not easy horses when they first come in.
To address your specific concerns, my horse does have a big thick neck and throatlatch, and it does make it harder for him to go on the bit properly. His legs are shorter than they ought to be, but his barrel takes up my leg just great. He is smart as a whip - smarter than I am - and more dependable and practical than just about any other horse I’ve ever worked with. He has Opinions and is not afraid to share them. He has pretty much zero work ethic, but then he’s a special case - wasn’t started until he was 11, after several years of neglect by his first owner. He’s surprisingly difficult to condition, mostly because of that work ethic. (It’s tough to do enough trot sets to get him eventing fit when you have pitched battles about even trotting forward.)
Here are some conformation pictures so you can get a sense of what I’m talking about: http://beljoeor.blogspot.com/2013/12/5-day-challenge-day-3.html
They are awesome, awesome horses, but you need to know what you’re getting into.