the thing that amazes me is that it takes 2 pilots for the b-29

That would depend on how many functions it has. Most R/C transmitters are limited to 8 channels. It's probably much easier to handle with two pilots. The full-sized aircraft has a flight engineer to look after the engines.
Not sure which was more amazing there, the size, the fact that it flew, or the beautiful landing that it made! 8-)
It's a scale model of a real aircraft. If it was designed properly there no reason it wouldn't fly. Most models are overpowered compared with the full-sized aircraft. Any scale modeller will tell you that the larger the model the better it flies & the more realistic it looks.
I'm not convinced that either of the models in the vids can claim to be the World's Largest Model R/C Plane. I don't know the dimensions & it depends on how you judge the size. This C-17 is 10% scale & has a wngspan of 17 feet.
http://www.largemodelassociation.com/davie_mathews_c17.htmThis DH.88 Comet is 50% scale & has a wingspan of 22 feet. Although the full-sized aircraft is much smaller than the C-17 the model is considerably bigger.
http://www.largemodelassociation.com/steve_holland_comet.htm