I sit mine right on the cover. Even my "retrofit" which I said I was gonna mount on a hood....and never did....sits right on the glass cover.
As far as hardscape...it's whatever looks nice to you. You will change it up until you find what is pleasing. I personally like a little rock and driftwood. I have a few nice river rocks that I have superglued java fern to....love them. I have a piece of driftwood wrapped in moss that my apisto babies love to hide in..you play around and look at other peoples tanks and go for it!! If you decide on a crypt...just remember no matter what size it is when you buy it, it will melt. Everytime you move it, it will melt. So just remove the leaves as they die, but leave the crown and before you know it, you will see new growth. They are worth the wait in my opinion. I saw one guys tank on aquariacentral and he had glued pennywort to a piece of driftwood...it was stunning! This is the FUN part!!