As above. Want to swap stuff between two bikes, as I’m struggling with the gearing on the new one on steep climbs. Havent checked the BCD yet, but if they are the same, will it all still work?

Old bike is Ultegra 10-sp with OEM Shimano crank 34/50, new one is Ultegra 11-sp with Cannondale Hollowgram cranks 36/52

Old ones had standard and compact BCD. New ones only have compact BCD. BCD only really relevant if you want to swap chainrings between chainsets.

11 speed chain will work fine on a 10 speed chainset.

What do you actually want to swap between the two bikes?

Just swapping chainrings. So its the 11 speed chain on 10 speed chainrings and vice versa which matters.

Ta!