Will prepping for the level I exam help at all with prepping for the GMAT (not at the same time)?
There is not much overlap - but there is some. I think prepping for the CFA has made me a much better student than I ever was before. I’m prepping for Level 3 and GMAT right now and having spent time on the CFA I have a completely new appreciation for just how much prep you can do to succeed. But other than that, no not really.
There’s probably some overlap in gearing up your math muscles and general study habits, but not much, no.
Maybe like 1% overlap between CFA & GMAT. Completely different tests and skill sets required to complete each exam. The GMAT is not an IQ test but it comes close to falling in that category.