Suppose:
I take the minimum required of troop type X.
The army list allows me to regrade some X to Y.
If I regrade some, have I still met the minimum requirements for X?
Example: 3534 Khazar
"Royal Army Horse Archers" have a minimum of 8
"Regrade Royal Army troops fighting like Muslims" has a max of 8.
So would it be legal to take 0 "horse archers" and 8 "fighting like Muslims"?
Yup.