I use all at various times.
Stringers for just boilies when I want a varied presentation; I can push boilies close together, touching, to slow down dissolve time and have 2 baits (or more) away from the hookbait, looking like a hookbait.
I do use mesh for just boilies, but I can also add chops, pellets, dry or dampened Vitalin etc. I can tie it off at both ends, one end to the hook, and the other to the line above the lead, or just attach to the hook.
I prefer bags around weed, when I'm not 100% sure that it will be right on the lakebed. A solid bag will, unless mega thick weed, get to the bottom and 'push' the weed down giving a presentation. This is where a small pop-up in a bag works.