Had a 7 night BRG claim approved for hotel A. Getting the claim approved was like pulling teeth and took 2 days:
1st email said "I am unable to approve your claim because the comparison site is sold out during your stay period.", I replied with screenshot and detailed searching steps showing that wasn't true.
2nd email said "I have reviewed your claim again and followed your instructions. Unfortunately, I was unable to duplicate what you are seeing. For this reasin I have no choice but to still deny your claim."
At this point I realized the site I used probably showed different results depending on location (when I searched for international locations I get redirected to a parent site), so I pointed that out, attached a new screenshot of an even lower price, and replied asking them to forward the claim to a colleague in North America.
The claim was then approved.

Now we are considering spending the first 2 nights at a different Marriott hotel B and reducing hotel A stay to 5 nights (a nice-to-have and not a must-have, especially with the new promo giving bonus per stay and at different brands), what does everyone recommend we do?
For hotel A, can I book a new 5 night stay and submit to BRG while keeping the overlaping 7 night reservation in case the new BRG claim gets denied, or do I have to cancel my approved 7 night stay first? What's the chance of my new 5 night stay not approved? (The lower price is still showing on the same OTA site, and has been for the past week or so).
For hotel B, can I go ahead and book to secure the lower price now in case it goes up, while I have active reservation for the same night with hotel A?

Thanks in advance!