great questions!

as the frame is designed to be FDM printed, the lasting nature of it will be solely determined by both your material of choice and the quality of your printer/slicer.

The 5.7 though, specifically, is HILARIOUSLY low recoil and required the least amount of mass to succeed (and still hasn't ever broke).

The DB Alloy will inherently take up more space as it has both a magwell and a pistol grip / trigger guard for the AR FCG it relies upon. I wouldn't get too hung up on the side plates - they were a pressure vessel containment strategy that looked VERY cool, but were ultimately overkill for what absorbs energy (the trunnion primarily, as it holds the barrel and the blast, and the backplate secondarily, as it just bounces the bolt back and forth from the remaining blowback force)