As far as your first question goes concerning the leather quality, I would advice you to contact them yourself via Facebook or Mail! They are surely happy to help you!
Concerning your second question: I own an IPhone 6 and a Joli Smooth Leather Sleeve. Initially I planed to use it together with a Spigen Airskin which is only 0.4mm thick. But the Joli Sleeves have such a tight fit (which is a good thing I think) that even 0.4mm is way to much on top of the iPhone form factor. I mean it works..but you have a really hard time to get the iPhone out of there!
What you could do is ask them if they can consider a glass protector when they make the sleeve for you!
Hope I could be of help! I'm very happy with my sleeve btw!
The smooth leather is softer and slightly thinner. I went with the textured because I really wanted a black sleeve (as opposed to grey), loving it so far.
The smooth leather is softer and slightly thinner. I went with the textured because I really wanted a black sleeve (as opposed to grey), loving it so far.