If you want no air in your loop, have a tee at the top of the loop and don't have your reservoir low. I always put a quick connect on the top of the case for the high end of the tee. I also put a quick connect out the back of the case below the rest of the loop. Makes fluid replacement much easier. To drain, put system on desk, put bucket or pot big enough to hold all the fluid below the desk, quick connect a drain tube to the bucket and the let air in the top with a quick connect.
Frankly, with a moderately large top tee, there is no need for a reservoir. I happily ran without a reservoir with my configuration. The trick is when you fill: you fill from the drain tube - I have a half gallon plastic pitcher with a tube from it's bottom to a quick connect. I set it on top of the case and pour in distilled water until I see the water nearing the top of the tee tube. Maintenance done.
I do not mix metals in the blocks. Go all copper or all aluminum. Distilled water only, additives are asking for corrosion or biotics.
All this said, I learned this on water cooling dual athlons as that system was painfully loud air cooled given the stated of air cooling at the time, and this configuration still works.
Air cool first, water if it is too loud. Loud is relative: I suffer severe tinnitus due to working in data centers in the 90's and the 00's, so any white noise is too much.
Not that it matters, a waterblock works just fine.
