hi, is it possible or is there hardware limit that one could have support for B1+B3 band CA support for this modem?
Those bands are 2100MHz&1800MHz on my country.

NO, that LTE mPCIe module cannot do B3+B1 or B1+B7 :(. Only B3+B7.

Of course B3/1/7 + B8/20 works but this is fast&slow game.