After reading Flamingo's answer in the mod's comments I've just found out how to edit SFO caps. I have read a bit how to use the Package File Manager and know some programming by myself.

You just need to copy and paste some chunks from "export_helpers_tt_groups.lua" into the SFO script with the very same name.
But you would need to edit all units you want to change the cap though. Apparently SFO uses a big chunk of this mod which you can find the same lua script to copy and paste from this mod into SFO, just make sure to skip the section which include "SFO unique units" right at the start.

Some units need to be brought manually as they already exist in-game and are not on the separate sfo units section such as "Gate Guards". Those will be lost if you copy and paste the big chunck of data/tuples that are in the TTC's lua script.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2017703134

If you check this image you can see it might just work very weel, I have only manually copied HE gate guard's cap and the rest of all the regular original WH units can be just copy and pasted apparently. You can even copy the "export_helpers_recruitment_control_monitor.lua" to show off the caps in the army's panel...

As you can see it is charging me 2 special pts for Ithimalr chariot and 1 for white lions
And ROR PG and DP both cost 2 points as well

I would like to know if this is even allowed to do and if so I could help porting this mod into SFO.