My only experience of Fulcrum is via two Planet X purchases.
When I bought my first gravel bike I upgraded from the Fulcrum 900’s to 700’s, mainly as +300g lighter for not much more and then when I bought a new gravel bike (Free Ranger) I just went with the supplied 900’s as I was going to buy a far nicer pair (and the original 700’s were QR).
The rims aren’t the easiest to tubeless, and when I looked at the Fulcrum website they admitted that they only recommended tubeless with a very limited tyre range.
No idea about the 5 DB, but worth checking.
As it is the 900’s have done service with tubes & slicks – best part of 2kg so now looking for some nicer wheels for slicks too.