I won't bore you guys with the details, but this is kind of a vague question, because one machine can be set up and running so differently than another with the same brand and size of blower.
That said, on a CTS 450, I would make use of your 2" Y to optimize your vacuum, run two hoses out as far as you need to reach the door of the job and go single 2" form there, then you will have a super sucker instead of wonderin' if two wands running at 60% will cut the mustard...or not.
I will say, the RX with
glides seems to perform much better than you would think on a #4 blower system when running two of them. The key is to not break seal, and keep your hose runs short.
So maybe there is hope for the dual cool Chem-Dry guy.....especially if he added supplemental heat.