I find idle engineers really useful - e.g. if I need engineers in an area to build pd in an emergency,and I have a mix of T1 and T2 engis, I can find the T2 faster with idle engineers; while the right hand default UI for idle engineers is it only (I think) allows all idle engineers across the map to be selected by tier, not idle engineers only in your screen
I also find advanced strategic icons REALLY useful for detecting TML and SML at a glance (and every second counts if you don't have defences up), as well as enemy radar.
Then again, I'm nowhere near 2000 1v1 rating (but I've found my performance notably better with these two UI mods.