All depends on when you start, how fast you are and where in the race you are. It does seem characters early on have longer lines, like the Nightmare Before Christmas characters always looked like a long line when I went by starting in the middle & they were before TTC when I ran it, I think, correct me anyone if I'm wrong on that spot. Lines should move fast as they don't sign, but still can get long, I guess each person takes what 20 seconds, maybe a little more, so if you can't see the end of the line, it's probably going to be a longer wait. More popular or rare characters can have longer lines it seems. But near the later parts it does seem lines are shorter. Oh & characters do go on quick snack breaks, so that can add line time as the grab something real quick
In 2015 a few of my stops in the first half took around 8-10 minutes, one was a huge villain group (which they haven't done since then) and the other was golf Goofy and Donald. But then like Chip and Dale at Wide World of Sports, so around mile 18/19, was like 0 wait. I was middle of the pack with a clock of like 5:20something that year.
But, in 2016 I was back of the pack during the race even though I started in F, and I finally stopped for Boo in Studios with like a 1 minute line and Scrooge at EPCOT like 30 seconds wait. Lines at wide world for characters looked to be a couple minutes long but I skipped as I was so wanting under 7 & did barely with 6:50 net time & clock time 7:04. So I would say if you can bank some time early on keeping under 16, then in the later half you should be able to grab a short character line or 2 & be fine not getting swept. Characters are in park and on the roads too, so they are spread out all over.
As for bathrooms, some can be long and some not, I try to only use the in park ones and have been lucky and not had to wait. In 2015 I stopped at portapoties really early, like before mile 2 and it was at least a 5 minute wait, so now I just wait till in park. In 2016 I used some Frontierland ones and it was empty. Wide World of Sports I remember having lines in 2016, but I really have no idea how large those are inside as I skipped them. It seems everyone darts of early on to the portapotties or bushes to go after waiting in the corrals so long, so if you can hold it awhile lines should be better.
But of course my observations will vary with others based on where they ran in the race & what years even.
@Ariel484 &
@ZellyB have great trip reports from the 2017 marathon with lots of character stops that might be worth reading to get an idea!