It depends on what the sail is going to be used for. A "weekends-and-holidays" sail, doing less than a thousand miles a year, can be made by "quick'n'dirty" methods. An ocean-crossing sail, doing 10,000 miles a year - well that's a different story. Put in the time and effort now, and you won't regret it further on down the track. Making lap joints between panels, so that the stitching is in shear, is not in the least bit difficult if you use sailmaker's double sided sticky tape to assemble the panels first, and will pay off in longevity. A patch under the batten pocket will protect the sail against chafe from the batten. A patch on the other side will protect the sail against chafe from the topping lifts. A wide doubler down the luff and leech will help to stop the cloth fluttering, which is a source of breakdown. Multiple patches at the peak, particularly, but also at the batten ends, spread the loads out into the sail and reduce stretching. And so on, and so on. None of this is wasted effort, if you want your sails to last, and keep their shape. If you're going ocean cruising, you need to do the job once and do it right, rather than having to keep going back to add more strength.
With webbing, strength and stretch are not the issues. Anything you can buy will be strong enough, but polypropylene has poor UV and chafe resistance, so don't use it. At the edges of the sail, it's not so much about stretch and strength as about protecting the edge of the sail from everything that is trying to fray it. Doubled over webbing does this job very well, but it's more difficult to sew on 1" webbing. 2" webbing is easier. I like webbing loops that go around the batten ends in shallow grooves to tension the sail, and I like webbing loops for sheet attachments. A sailmaker here in Tasmania (who is making his first junk sail, from Odyssey) tells me that he much prefers Dyneema webbing for this kind of usage, because it is much more UV and chafe resistant, and is much stronger, so very small sizes can be used. I don't like webbing loops in place of batten pockets, because it takes me a lot longer to stitch them on.