I’m positive a hydraulic autopilot on your main with trolling bags would troll well. I did a ton of research on these APs when I was choosing. The only one I’d avoid is the Garmin ‘compact reactor’. Their literature specifically states it’s not suited to slow speed operations. The regular Garmin reactor is good to go. I chose Raymarine Evilution because I found lots of positive comments from trollers on various forums. Seeing how it works, I don’t think it’s anything special though. Garmin Reactor, Raymarine, Furino, Smirad, Lowrance should all work. Trolling with bags gives very good control because the bags stop the boat from surging while the motor is producing lots of thrust. I’ll troll that way in April when I’m trying to stay around 1.5

I did the conversion to hydraulic steering and autopilot install myself. The difficult parts of that were 1) rigging tubes couldn’t handle three lines from helm to stern 2) needed odd/non standard hose lengths to do a ‘clean install’ and 3) needed additional fittings/elbows to connect AP pump to sea star fittings. The pandemic started around the time I started this install and shipping was slow early in the pandemic. The key to making custom length hoses is this fitting:

Hydraulic Steering Hose Reusable Fitting, 5/16", 2TFMS-6-5B