I honestly doubt he sprinkled backpacks around the city--it just doesn't seem super in character for this guy, and we don't have any video evidence of him from prior days sporting different packs (the pack he wore was rare-ish, and buying a bunch of them would be detectable to LE...). But I did consider the notion that he could be depositing them around Gotham like some megavillain out of a Batman comic (The Stoodent strikes again!)...
I do think compared to most, he had so much money. A very expensive weapon, perfect teeth, higher end clothing (his jacket alone cost $695), a $400 backpack... I think he chose his transport and lodging not to save money, but pretty carefully to avoid detection--where he could get away with using undetected fake IDs, pay cash, come and go unencumbered.
But moreover, he comes across as a killer "for the people" with his anti-insurance messaging, and the the hostel/bus/e-bike/train. I honestly think it's a very carefully crafted image, right down to the words on the bullets. No sooner did people hear the words "CEO United Healthcare murdered" than began the jokes...
This may be one of our first "celebrity killer", honestly, if not the first. A blend of reality TV and Robin Hoodism, made possible buy the clear video of the crime transpiring, that is terribly scary because yes, as you say, we are all vulnerable--and not all would be criminals of this ilk will be as precise in hitting only his chosen target.