The weight of the rim is not so critical for strength these days, since thin extrusions can be made reliabley. Lightweight rims will wear out at the braking surfaces more quickly.
The number of spokes is significant. A standard road wheel has 32. For heavyweight riders, loaded bikes, hard use, or a more reliable ride, 36 spokes are stronger . You can use 28 spokes on a conventional wheel for light riders, who can ride responsively, but if it goes out of true, it will go big time.
Since the rear wheel is more heaviliy loaded than the front, it makes sense to use a stronger wheel. The trad touring set was 32 front/40 rear. Some people make light-touring/commuting sets with 32f/36r.
What really counts in a trad spoked wheel is the build quality. I'd take a pro-built wheel made of low-end components (ie my commuting wheels) rather than a machine-built high-end set.

When you start using direct-pull spokes, plastic spokes, or any funny stuff, then you can probably ignore the traditional spoke advice. Just dont expect to be able to fix them by the roadside when something goes wrong.