First 4 linens are up for custom:
Twill is one of the most naturally wrinkle resistant fabrics out there, I'd be extremely surprised if they were comparable.
Linen is going to wrinkle, its supposed to. Its part of the look, cut it a bit looser and enjoy it. Linen has great surface texture so a few extra wrinkles don't do too much damage.
Perhaps try some of the cotton/linen Rick has incoming, should resist wrinkles a bit more. I love blends like cotton/linen, wool/cotton (not shirting usually). He posted some a few weeks ago.
Linen is going to wrinkle regardless. It's part of the characteristic of the fabric. But surprisingly, this particular linen wrinkles less than a lot of other linen we've seen. It has to do with the weight of these. The body on this linen is pretty incredible.
No, I only have about 8-10 shirt lengths in each of the linen for Custom.
Yes you can do double breasted.