As Grincher says, the density will vary depending on the supplier and so unfortunately this is a bit of a gamble. But if you speak to someone at a decent supplier, like Eric at NWL or Richard at Ukhairsystems, then they listen to what you want and advise accordingly.
For example, NWL's light option sounds like it might suit you, or even extra-light. I ordered (from Ukhairsystems) a light density with an 'extra-light' inch at the front (graduated hairline) and it just arrived today - and it does not look or feel too "light" , so I am happy with it. It's age appropriate for me (I'm 44).
Yes the lighter density system will need replacing more often but with good care you can probably get 3 or 4 months use out of it. I know some people get more. Depends how you treat the system... keep it conditioned, don't wash too often, don't get it wet in swimming pools etc etc.
BTW if this company (who are they?) only offer 80% or 100% then that is a problem right away. I know, because I was only offered 80% and 90% when I bought my first system and so I went for the 80% … and it felt like 200% when it was on my head!! I looked and felt awful. So be wary of even the 80%. At the very least, ask to see what it looks like on someone else's head.
2 inch length is short, and I would suggest 3 inches because then you can eventually go shorter if you want to. If density is light then the hair will hopefully sit flat anyway and so the length won't be such an issue.
As with many things in life the only real way to learn is to dive in and begin wearing. It's great that you're here talking to us all, and like you I did the same: lots of research and lots of questions. But guess what, I still ended up with a nightmare of a system for my first attempt. But I worked through it. And you will too.
Keep asking questions, and start buying self-maintenance products like glue/tape, conditioners, shampoo, those little scissors that you can cut excess lace off with, 99% isopropyl alcohol, tweezers etc.
Good luck!