You can have both cards. Eligibility for the SUB will depend on which Chase and Amex cards you have open, when they were opened, and when you received SUBs on them. Chase and Amex both clearly state eligibility in the terms on the application pages, and they differ for each current product.
You can only receive 15 elite nights for all personal Marriott cards and 15 elite nights for all business Marriott cards (originally after the SPG/Marriott/Ritz-Carlton program merger it was 15 total regardless). If you already have the Brilliant, the only way to get more than 15 nights is to open the Amex Business Bonvoy (provided you didn't already have a legacy Marriott business card from Chase).
A maximum of 15 Elite Night Credits will be provided per Marriott Bonvoy Member Account, unless you have both an open small business Marriott Bonvoy Card account and an open consumer Marriott Bonvoy Card account; then, you may receive a combined maximum of 30 Elite Night Credits (15 per Card account).
Other than SUBs, one consideration might be to product change after a year to the Ritz-Carlton card. You can't apply for it, but you can still product change to it (once passing any Credit CARD Act restrictions, hence the 1 year wait). It's very similar to the Brilliant, but the extra 50k certificate each renewal as well as the annual credit would likely more than offset the annual fee for you.