Here's my UI. Almost 100% ACE except for Itemrack and MSBT.
The bar (Bartender3) swaps using either CTRL or ALT to lesser used combat buttons. There's a hidden bar down at the bottom that pops up on mouse-over that also can swap using ALT to the least used buttons of them all.
The UnitFrames are Pitbull with a lot of the modules disabled; especially the buggy Aura module. I've considered switching to ag_UF, but haven't put the effort into it yet. The pet bar is right about the BT3 bar that reveals itself on mouseover if I need it.
The main Quartz bar appears just above the target frame and the debuff trackers show on the top-right side. Enemy castbar shows at the bottom of the target frame.
I've tried to be as minimal as possible, but still have the necessary information available. About the only other thing I can think to do to minimize further would be to scale down the minimap further (it's at .90 now) and autohide the Itemrack and Autobar on the right.
If there's any other questions, feel free to ask. And if you have any suggestions, I'm open to them.