I will try and stick to your specific questions.
To adjust either type at home is possible, neither is more difficult but have different techniques. On that basis I would say to choose freely, and learn how to maintain the one you own with a good how-to book or online videos etc.
Disc brakes do not stop you any faster in the dry, but do potentially help you stop faster in the wet, as the braking surface does not go through puddles and mud.
Personally I think that cable disc brakes are easy to maintain once you know how. You need the disc to be straight and true, then install the caliper so that the pads centre around the disc. You can adjust the 'fixed' pad with a 5mm Allen key and the 'floating' pad with the tension in the cable. The floating pad is the one outboard which is moved by the cable. On mechanical disc brakes, only one pad is moved by the cable. As the pads wear down you can adjust both sides to move the pads closer to the disc once more. Pads might be more expensive but you might judge them worth the expense. If you're concerned about being far from home in need of pads, take spares along with you.
Rim brakes are also possible to maintain at home with the same tools, the pads need to be installed carefully to line up with the rim and not touching the tyres. Also to keep them quiet, they should be toed-in. Then you set the cable tension with an Allen key to make the pad spacing correct each side of the rim. Small screws on each brake arm allow you set the spring-back of each arm individually. Then the brake will spring open again correctly.
Fine adjustment of rim pads can be fiddly, but you can learn in the warm and practise.
Now, neither type requires much in the way of specialist tools, except for further maintenance like keeping the rim straight (true) or keeping the disc rotor straight.
So Yes a layperson can maintain either style of mechanical (cable-operated) brakes.