Sounds like a plan. I'd mess with the metal frame for the storage stuff first. Actually put it in place, secure it and put the stuff on the shelves to see if you have enough storage and if you have to adjust any to make room for the vacum cleaner or any other odd shaped objects.
One other suggestion would be to make sure you label your storage containers clearly BEFORE you put them on the shelves. Maybe even take pics of what goes in each box and either put it on the outside of the box where you can see it or put it into a file and just number the boxes and the back of the pics so you can find stuff.
If it's going to be a cat playroom you are going to have to make sure the cat can't crawl into the boxes or lay on top of boxes and damage items.
My favorite rod holders are btw ones used in closets. The one end is open like a letter "c" turned on its side so you can remove the rod should you need to so you can clean/replace as needed curtains.

I just put up a wide 2 panel set of curtains on a spring rod, but also used thin wire in the middle and both ends tacked to the ceiling with small screws just in case the thing ever slips at all. I also have storage in there (along with a small hanging clothes rod. It looks great and was easy to do. I also have active cats, but they're not much interested in the stuff, having other high places to play, and the only 'casualty' so far has been a long sweater off the clothes rod (it's lower than a regular built-in).