Can you speak to what issues you have with the AtomStack? Might help in assessing whether or not one of the alternatives would address your concerns.
Assuming you’re working with dark materials (ie must be optically opaque to the laser wavelength) .5 mm will cut without much fuss on the Ortur. The 3mm is doable but at higher passes and/or power. If you’re doing high volume work at 3mm then you’ll need to work out if the performance is sufficient for you. Anything more than the occasional cutouts at 3mm I’d suggest you look at a CO2 laser.
Camera choice is less about the laser than it is about your environment, I’d say the enclosure in this case. I haven’t seen any specifics on recommendations for the Ortur enclosures although there have been other topics on this. You may want to do a search.
I’m not familiar with the enclosure dimensions but this could sit between the legs of the laser frame so that you wouldn’t need to trim the ends.