I got the 1060 w/3mb RAM and am currently running OpenALPR and DeepStack on the GPU with excellent results. If I were doing it again, I'd buy the 1060 again only with 6mb RAM instead of 3. OpenALPR only has 1 camera feed at this time, soon it will double. DeepStack is analyzing feeds from 10+ cameras.
From everything I've read here and at the DeepStack forum, while there are many versions of the nVidia card that will work, the 1060 offers a very good balance between performance and efficiency. My system runs 24x7 so if I had one of the higher performance cards such as the 1080 or the new 30-series, the GPU would be sucking far more energy and have so much performance headroom it wouldn't be sensible. Yes, it would be faster, but my DS times are already sub 50ms, so the incremental improvement would not be worth the extra power demand, not to mention the initial outlay for those high-end cards right now.
Having said that, my system is pretty robust in that my CPU is an i9-9900k. Not the latest in Intel chips, but still pretty beefy compared to most. Whatever you are running as a CPU will likely play a part in your selection of GPU cards.