"Also, does 27.5" or 29" make a significant difference? The bike in the video is a 27.5" I rented."
26, 27.5 or 29 wheel roll just fine. But do they make a difference? Unfortunately yes. 26 are more nimble in the corners, 29ers are better in rolling over terrain because of the big wheels and 27.5 is a good compromise between the two.
26, because of the smaller wheels will be a be a bit rough compared with a 29er on rugged, technical trails but a 29er will be more difficult to maneouver in trails that are twisty and turny. 27.5 is the middle ground and is said to be a good compromise.
at least that's what my friend who rides for a living said. I ride a 26er enduro bike right now and it does just fine. Imo... get what you can lay your hands on, proper fit, and just enjoy!
Thanks for the input. For this particular trail, I'm thinking a 29er would really help with rolling over the rock gardens. Clearance height would help too, every run my pedals will hit the rocks at least a few times. Is clearance height an issue for you on your 26"?