do you have an complete schematic
use a dropbox or an web site tho host it.
I find this psu overthink-ed for nothing, using power mosfets for voltage regulation, the only advantages is to have a very low RDS (resistance drain source) the lower the better, they will dissipate less compared to power transistors.
Mosfets are generally controlled in current, so don't think in voltages all the times. If you psu is max 40volts out, the gates at pin 1 may go up to 10 volts
not 40volts, see it like an amplifier, 10v multiplied by 4 ... gives 40v
I do think Q17 and Q21 are the output current limiter for the mosfets ... not necessarily the main current control section, i don't see where p14 goes
Your question about the two facing op amp with diodes : many power supplies with CV an CC are made like this, one op amp manage the current section and the other is the voltage
The amp limiter section thru the diode will affect the common point of the diodes and can negate or lower down the voltage etc ... depending of what you selected.
The blue line is the final one going to the power stage transistors
But since i don't have the complete schematics i do guesses.
My guesses is on P21 with the aci and avc line ...
Have you asked the company for the schematics