Yes,the size of the battle you play matters.You'll get more points for playing a medium QB,let's say,than you get for playing a small one.
The number of points you get is computed using this formula:
Points=Victory Level*Size Modifier(SM)
The Victory Levels are:
Total Victory-11
Major V-10
Tactical V-9
Minor V-8
Draw-6
Minor Defeat-4
Tactical D-3
Major D-2
Total D-1
The way the SM is determined can be seen here:
https://www.theblitz.club/scenarios/action=sm#CMBN
Basically,the larger the battle,the larger the SM will be.For a Small QB the SM is 3.For a medium QB the SM is 6.In effect,this means you'll get double the points for playing a medium QB than for playing a small QB,assuming the victory level is the same in both cases.