My Salsa Fargo is currently running drop bars with 1x brifters, mechanical disc brakes, full housing.

I have a flat/alt bar and have brakes and flat bar shifter that work with the RD.

I’m wondering if I can just loosen the pinch bolts on RD and brake callipers, headset cap and stem bolts on steerer tube and remove the whole thing, without removing anything else? I think this is possible but maybe I’m missing something?

Reason is I want to try the flat/alt bar set up again but with a different stem. I’m thinking I put new cables and housings on that set up and install it, adjusting RD only.

And if that doesn’t work, back goes the drop bar set up. This saves me unwrapping and re-wrapping bar tape, and trying to re-use cables and housings between two set ups (vs, one set dedicated to each cockpit).

If this worked, I would use the flat/alt bars on trails spring through fall, and then have my winter road bike set up (in winter).

Anyone ever do this? Drawbacks? Thanks!

If you have some extra brake and shift cable housings lying around, then yes, you can remove the drop bar /brifter in one piece without unwrapping the handlebar, and install the new setup.

Brake cable pull - assuming the current levers are road pull, do you have suitable flat bar levers or are you intending to swap the whole brake system?

road levers are short pull.. flat bar levers are either short (Canti or Side pull, mostly Old brake levers)or long pull (V-Brake or MTB Disc)...
Avid makes convertible pull ratio levers. "Avid Speed Dial" are variable.

check caliper pull by measuring from the center of the pivot point on the caliper arm to the cable clamp surface...
30mm or so is short pull, 36mm or more is long pull.

check lever pull by measuring from the lever's pivot to cable pull/pivot point.
if the lever has a cable stirrup, use the stirrup's pivot pin at the lever...
26mm or so is short pull, 32mm or more is long pull.

the brake Cables will be the MTB style.

Hi. It’s Sram Apex 1x and the flat bar shifter works with the Apex RD and the brake levers work with the TRP Spyre (I’ve already used all these parts, just didn’t like the fit with the bar I tried). My question is around easy if the cockpit swap (cables, housings).

Should be easy then. It looks like that frame has all clipped/zip-tied cables so you can remove them without disturbing anything (otherwise I'd suggest soldering cable ends to make them easy to reuse when you switch back).