Insulating Steel 2x3s

Currently renovating my basement after some smoke damage. The basement used to be finished in the owens corning system, which means some of the areas were framed out with 2x3 steel studs, and the corning panels were affixed in front of them, creating both the wall finish, and the insulation. 75% of the exterior walls were just affixed right against the concrete, so moving from owens corning to traditional insulation/drywall i've already glued Foam board insulation to the concrete, attached furring strips anchored through into the concrete with ramset nails/tapcons, installed vertical furring strips for framing, and i will drywall against that, but i'm still trying to figure out how to reuse the areas with steel framing that exists around things like the oil burner room, and the room currently used for storage and washer/dryer. I dont really have room to affix foam to the concrete wall in those areas due to a combo of both lack of space, and placement of electrical service, oil tank, plumbing stack etc. and i have no intention changing the layout, so its ideal to leave the framing in place

So my option is either placing 2.5" insulation in the cavities between the studs, and then drywalling directly onto the studs, or foam board in front of the steel studs, and then drywall over that. Both would in effect isolate the unfinished colder basement spaces of the oil burner room and laundry room from the finished space, but just trying to figure out what's easier and more logical.

I know the steel studs act as a thermal bridge, so the ideal situation is insulating behind, but at least in the oil burner room, its so tight i would have to remove it all and start fresh which is more work than its worth for a basement.

Is the solution glueing 1" of Foam board in front of the studs with foam board adhesive, then adhesive on the back of the drywall, attach drywall to foam, and then drive longer drywall screws through and into the metal studs. Seems like thats the easiest method so long as the strength is there to hold everything

 

Use spray foam kit (Froth-Pak, etc.) to fill the cavity between/behind steel studs and then install drywall.

Foam board in front then drywall will also work. Glue foam to stud only to keep in place until drywall is installed but not necessary. No need to glue drywall to foam. Long screws through drywall and foam board into stud will work.

I needed to increase R value when converting attic to bedroom space. On top of Fiberglas in wall cavity I installed 1.5 inch foam board on face of studs with 1/2 inch drywall using 3 inch DW screws. Great for insulating--PITA for mounting electrical boxes.

 

I should have specified. The steel studs are not flush against the wall. They're framed out as the exterior wall closing off an area. So If the burner and oil tank are against the concrete wall or within a foor or two, the framing is another 2-3 feet in front of them creating the exterior walls of the enclosed room. So the only way to use spray insulation would be to put some kind of backing behind it, again difficult in some spots like the oil tank which is inches from the steel studs and impossible to crawl in there, let alone affix anything to the back of the studs to provide a backing.

So i guess it looks like insulation board + drywall + screws is the easiest solution