Might have been useful to list the resistor values for the 200MHz "working" configuration...
There seemed to be some other fairly obvious config/build version resistors, two sets where only one of two R's was populated.
It would be interesting to see what, if any, differences you see in the outputs of the 74HC595 near the front-end.
I had a brief look, and there is a mux in there so it could be it's selecting between full and limited-bandwidth paths.
Didn't see anything that looked like a Rigol style varicap,