I don't know how you didn't see the difference between the packages, but referring to the -dev prefix, it is for when there are beta versions, pre-release, etc...
mhdi [1] filed a deletion request for droidcam-dev [2]:
This package is a duplicate of aur/droidcam. The `-dev` prefix in the
package name is redundant, since there is no upstream dev release. The
main difference between this package and aur/droidcam is that the
latter installs the binary to /usr/bin, while this one installs it to
/opt.
[1] https://aur.archlinux.org/account/mhdi/
[2] https://aur.archlinux.org/pkgbase/droidcam-dev/