Choosing hubs and rims for training road wheels I'm going to build a training road wheelset for my touring bike. I wonder what should be criteria for choosing hubs and rims and spokes. I'd prefer cheaper options as long as they are durable and not too heavy.

Hubs: which are considered serviceable as opposed to disposable? And which require relatively little maintenance? My bike has 135mm rear dropouts, so I need MTB rear hub, but for front - search for MTB or road?

Rims: there are many budget models with slight variations in weight and strength. I'd like to find one with maximum strength / weight ratio, but how can I estimate the strength? Say, AlexRims DA22 is advertised as butted but it weights same as 1.5x cheaper Mach1 non-butted rims. Is butted any better if it's not lighter?
Front hubs on mountain bikes and road bikes are all the same width, 100mm (except for some downhill hubs with through-axles). So you could use either type, they would fit in your forks fine.

Note nearly all current mountain bike hubs are designed for disc brakes, so include mounts for attaching a rotor. You can still use them on a bike with rim brakes, just don't fit a rotor. The disc part would increase the weight a bit, so they will be a bit heavier than an equivalent road hub. Also the disc mount means the hub is not symmetrical, so the wheel has to be dished. This makes it a bit more complicated to build, ie it needs different spoke lengths on each side. But this doesn't really matter, you can still build a strong wheel with either sort of hub. And disc mounts would be useful if you wanted to fit disc brakes in the future.

As for which hub, generally mid-range Shimano hubs are good. eg Deore or LX for mountain bike, or Tiagra or 105 for road. Usually they just work fine for years, with hardly any maintenance. Shimano hubs typically use cup-and-cone bearings, so they can be serviced, and the bearings replaced, but this may be a bit fiddly.