Hi Haseo,
The primary reason to plant lilies deep is because they are stem rooting (roots grow out of the side of the underground portion of the stem as well as from the bottom of the bulb). These roots provide extra nutrition over the growing season (so your bulb gets larger) and add stability to the stem.

Deep planting also helps prevent premature sprouting (and hence frost damage) if there are wide temperature swings over your winter. It also helps keep the squirrels from getting them.

Stargazers are fine at 6", but if you haven't planted them yet I'd go ahead and put them 8" or even 10" deep.

I'm not understanding the second part of your post. Different lilies have different leaf patterns, but all have a good amount of leaves. Compared to an Oriental (like Stargazer) Trumpet lilies have a large number of thinner leaves and Asiatics have a somewhat greater amount of leaves. Without more info. I can't help you.

Also consider scent, Orientals and Trumpets have a strong scent. Asiatics are usually scent free.

-Helen