Yeah, I'd go with hot smoking on the trail and I'm not afraid of backwoods plumbing – I've brought hot tubs on backpacking trips. But cold smoking like to make lox is so involved and you are really counting on the smoke and brine to preserve the fish unlike in hot smoking where you have belt, suspenders and second belt of smoke, brine, and heat to preserve the fish. Also, hot smoking results in a lighter product that you won't have to keep as refrigerated to pack it out.
For wood chips in a hot pan on an electric element, you can use any chunks of hardwood or fruit wood. Apple is good, Alder or Hickory are common. You can buy shredded one-pound bags that are between chips and sawdust for the electric smokers. You want a lot of surface area for your "chips" because only the outer surface chars and makes smoke.
Since you have apple wood at home, clean up around a chop saw or table saw and then make cuts every 1/8" to turn the whole thing into sawdust. Sawdust gives more smoke per minute but needs to be replaced more often than larger chips and sawdust should be used in thinner layers.
A bunch of things are going on in hot smoking. Salt, sugar and smoke are themselves preservatives, but they also osmotically draw out more water from the fish. That helps preserve the fish and reduces its weight.
I'd ignore any recipes that call for a liquid brine because that's very wasteful of salt and sugar and generates a lot of waste brine. I'd go for dry rub of salt and sugar and maybe use a pack towel to dry off the "sweat" that comes out of the fish into the dry rub. Then take off the rub and go on to hot smoking.
Test any procedure at home on small quantities of store-bought fish. Bracket your recipes (best guess, more salt, less salt) and see how you like the results. KEEP NOTES. In a few runs, you'll be dialed in and know how many supplies and how much time to take when in the woods.
Alaskan Natives set up their "fish camps" each year for weeks at a time and process on site. I get my sockeyes only 4 miles from home, so I work in my kitchen. But I like the idea of processing your catch as soon as possible. One year, 500 miles from home, I vac-packed on the beach and then froze the fish on the drive home using ice chests of ice plus salt – like you'd use to make ice cream at home.