any benefit due to balance in nbdb portfolio

Hi, I have a nbdb brokeage account jointly with spouse and our RRSP/TFSA/non-registered etc. Have banking with bmo where we need to keep 6000$ to avoid fees.

I was wondering if ndbd investments helps to get benefit on credit card and monthly banking account fees from National bank?.

Anyone sees any risks of having relation with single bank vs two banks?

thanks