The 1X gen-1's are the brightest and clearest, and have the widest depth of field so get as close to 1X power as you can. Most use a visible-red jumbo LED for illumination, so you are not "invisible". You can change this to an IR LED yourself but that will not show as brightly as the red LED does. Gen-1 NV's usually need some illumination to be any use at all, unless the sky is clear and the moon is about 1/2 full or more.
Overall, sometimes gen-1's can work pretty well, but other times they are useless.
Some of the cheaper ones use very-poor quality tubes and optics, and are always useless.
Gen-2's work way better, but then a decent new gen-2 will cost you $1200 or so, $1500 with a head-mount.
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