The form-fitting ones specifically for your phone model are decent. The clip on ones suck. You'll have a reduced field of view with the cheap clip on things. the form fitting ones should make full use of your camera lense and scope.
Regardless of which you have, holding a camera steady with 30-60x zoom is nearly impossible. You'll want something to hold your camera steady while you take a photo, like a string hung from tent bar etc or just buy one of those desktop digitial microscopes, but you can only takes pictures of things you prune off with those.
If you had an articulating arm that could attach to tent pole and hold phone steady, that'd work very well. Not worth the investment imo, but ymmv.