I know there was a topic at some point about what measurements make a sofa comfortable, but I can't find it.

How does
87.5L x 39D x 37H s
seat height 20
arm height is 32.5
sound?

The seat and the arm rest look too high for me (current sofa height 16" so it may be the difference throwing me off).

The arm is obviously too high to rest the hand. Can you rest the hand on the bolster?

Is depth normal? Back height?

That is a pretty sofa and yes you can rest your hand on the bolster but remember that the bolster will be taking up room.

I was looking at sofa's last weekend and some have a very long depth for the seat as in my feet wouldn't reach the floor and I am 5'6" 1/2. Others were very short where most of your leg wasn't on it.

Don't know if you have looking in furniture stores or just online but I would go sit on them before I bought because some of the very expensive ones weren't comfortable to me and other cheaper ones were but not always. My back got tired of sitting on way to many and came home with nothing.