its worth noting few bigger lasers run at anything like there stated power levels on a lot of material - gas - thickness combinations, this especially goes for steel being cut on oxygen. You can also laser cut thinner steel on air too, its commonly done on aluminum, but it can give you a pretty clean cut half way between oxy and nitrogen for a lot less cost on consumed gasses and the extra power it typically takes to cut on nitrogen. put simply with air or oxygen, you get the added heat of the burning metal and that impacts cut quality and cut speed - needed energy input.
Cut quality should be pretty dang good, i would expect nice sub 1/8" holes on 18 guage sheet laser or plasma, laser will happily pop 1/16" holes in 16 gauge materials and hold a +- low single digit thou toerances doing so, plasma will get you nearly that too if your motion control is good enough. Tolerances may vary a bit more with the plasma as the nozzels wear bigger, laser, especially cutting with nitrogen just don't do this as the nozzel simply never has the contact with the heat energy unlike a plasma nozzle than naturally has the plasma jet passing through it radiating a hell of a lot of thermal energy.
Hi def plasma rules for thicker stuff, really not sure what the cost of the smaller fibers will be as to how they compare to the cost of the plasma when the goal is this kinda thickness range. Have little doubt in time fiber lasers going to go after ever more of the plasma cutting market place.
Dross wise its really not going to be much even hypertherm air plasma leaves virtually nothing but a slide bead on materials at these thicknesses, if you use there fine cut consumables and can move the torch smooth and fast enough. My experience it rubs off with nothing more than dragging something else along the edge. You really need to get samples cut and price up options to make the decision as to what really works for you and your product.
That said, there's lots of contract cutting places out there, i don't run a profile cutter of any kind here as i can buy laser cut parts in so cheaply and my times better spent on making those parts into product than trying to save the grand or so i now seam to spend on profiles a month. My laser supplier buys steel by the lorry load, that gets you a level of pricing you just can't compete with buying even a couple of tons a time. trade off is lead time, but i seam to get a reliable 6 working days turn around with them and even if i had a profile cutter, here i would only get steel delivered twice a week by the local guys, hence really would not save much doing it my self.
