I've got 6 cams
2 of the Cuddyback 3000s - Nice camera and I like it best. It was my first.
I've got one crappy walmart cam - poor pic quality. No info on pic (not even time). I keep it set out behind the house where I can service it regularly. Don't buy one of these.
I've got one of the new Cuddyback excites. It is a good cam with lower pic quality.
Ive got 2 of the Cuddyback experts.
All in all I am pleased with the Cuddybacks. I think they are regarded as the industry leader.
I don't do anything special to secure the cams other than what was provided and have never (knock on wood) had one stolen. A lot of folks are not so lucky.
Never used an "invisible flash". I don't know that it is necessary as the flash doesn't seem to scare the deer (at least too much). I think some get used to it better than others.
IR flash is noticeable - red light that you can see.
If you want to catch a trespasser, disable the flash. For the most, part I think the trespasser would be out during daylight hours (never caught one on pic so what do I know).
Game cams are a hobby in themselves. I really enjoy checking the cams and usually can't wait till I am home to review the pics.
You can learn a lot there as well as read dozens of reviews on different makes/models.
I think the key features are without a doubt
1.) trigger time and
2.) pic quality. The cuddys excel in both of those areas from what I've seen.