I only did the Princess 10k but I did Dopey and I thought that the course etiquette wasn't too different between the two, even though I did the Princess 10k like 30 minutes slower than the MW 10k and expected a more packed course because of it. It felt like we were released so much faster for Princess since I crossed the start line like the same time as MW even though I started in B for Princess and A for MW. This meant the course was much more crowded at Princess for the first minute as there were a lot of walkers to weave around, the mini-waves must have been smaller at MW which meant less crowding at the start.
In general there were the occasional runners that would sprint when they saw photopass and run from behind and swoop directly in front of you with airplane arms (still don't understand this) but had this at both races despite running them very differently. So definitely not unique to Princess. There were some slow runners/walkers that were going 3-4 across in areas where they should have been 2 across and I don't remember this from MW however since I ran MW much faster (maybe 10 min miles between photos instead of 12.5 min miles) perhaps I just got ahead of those groups at MW.
Photo lines were sooooo much slower at Princess. Even the first stop I did where I hadn't "lost" much time compared to Marathon Weekend, it moved like molasses. People were doing full on character interactions. Hugging hello, hugging goodbye, miming and conversing. Then taking group and individual photos. And getting poses with the phone and then with photopass (pick one to look at and move on, people!). I don't remember this from MW, I just remember snap and go. I know I ran MW faster but since it was like this from the first photo stop we did, I think it was more of a trend at Princess. Mickey moved the fastest, I think because he was immediately going for the arm grab to take a posed picture, LOL! So definitely depends on the character/attendant. At the expo I thought it was interesting, Minnie switched multiple times while we were in line and one Minnie was very into hugging, interactions, escorting people to the photo and then back to their belongings. Very cute if the line isn't 100 people long but it was taking minutes per interaction. Then she switched out and the next Minnie was like hug, photo, move on! Ha!
All that aside, despite taking Princess 10k on the slower side (around 2 hours with 5 photos), since we started in B we had enough room to jog the entire course when we wanted to. It was tight on the path between Studios and Epcot but there was enough room to jog single file if you went around the folks going 3-4 across. But in other areas it was never too crowded. No diva attitudes, no one going from running to walking without warning, etc.
I still highly prefer MW after doing them back to back. Just the vibes and excitement about the running, I am not a super serious runner by any means but runDisney is definitely about running with a side of Disney for me, and not Disney with a side of running. Also it turns out I don't really have any interest in meeting Princesses and so I prefer the MW characters. I was so disappointed there was no ShellieMae after hearing Duffy was at the 5K
I kept passing the princesses thinking ugh - I could meet you in the parks with less of a wait! I should do the Princess half for more rare characters but the 10k is about the limit for the friend I do Princess weekend with.