—
Tried your capx on 2 laptops (both with r246 version of C2):
New i5-7200U, 8Gb RAM, SSD, Win 10 - project took 3.5 minutes to load, dialogs take 5-10 seconds to open, everything is laggy.
Five years old i7-3630QM, 8Gb RAM, SSD, Win 8.1 - project took 3+ minutes to load, but dialogs are opening almost instantly, previewing is also fast.
Looks like you are right, performance is much better on older machines.