As Zerk2012 already stated, tower-type air coolers act as an exhaust. So, very little of the CPU's heat actually remains inside the PC. Heck, GPU is the one that actually heats up the PC case internals the most (unless it's a blower-type GPU, which are rare nowadays).
Also, if you mount the rad at the front, the AIO will heat up PC's internals. And that far more than tower-type CPU cooler. So, your point of CPU air cooler heating up PC internals, compared to AIO, isn't true.
For other options regarding air coolers, here's a bit further reading,
article:
https://www.tomshardware.com/reviews/best-cpu-coolers,4181.html#section-best-air-coolers
Others not listed there, but still solid, are:
* Noctua NH-D15 / NH-D15S
* Be Quiet! Dark Rock Pro 3 / Pro 4
* Arctic Freezer 34 eSports Duo (this one is mid-sized CPU cooler)
I'm personally running Arctic Freezer i32 with 2x Corsair ML120 Pro red LED fans in push-pull conf. Freezer i32 is quite old now. But since i have Core i5, it is good enough for my chip.
With AIO, the idea IS to run the pump at 100% at all times. This way, heat is transferred away from the CPU as fast as possible, to the rad. Also, it keeps the liquid temp lower. But if you were to run the pump at e.g 50%, the liquid in it will get hotter and CPU can hit thermal throttle, since not enough heat is transferred away from it fast enough.
Downside of running pump 100% at all times is, that you'll burn through the pump's lifespan faster.
Noctua fans are solid. Given that you don't go with airflow fans and are actually picking the ones that have good static pressure.
As of being quiet, well, if you run e.g 120mm fan at 800 RPM, it is quieter than same fan at max RPM of 1500.
To get the best possible airflow with the least amount of noise, install as many fans in your case as possible. Preferably 140mm rather than 120mm since 140mm fan moves more air and does that more quietly than it's (same spec) 120mm counterpart.
While installing 5x to 7x fans in your PC may look like that you'd get extremely loud noise out of your PC, it's actually vice-versa. The trick is that the more fans you have inside the case, the less each fan has to work to maintain the airflow and the less noise fans produce.
And that is also a main reason why i have 7x high-end case fans in my Skylake and Haswell builds (Corsair ML Pro LED and NZXT AER140 RGB). Mostly 140mm but few 120mm as well. Full specs with pics in my sig. Since i have that many case fans, i can keep all of my case fans spinning between 800 - 1100 RPM and thanks to this, my PCs are very quiet while still having proper airflow inside my full-tower ATX cases.