There's no real need for manual control. Some ppl like the options some software can set for specific fan curves, but mostly it's plug-n-play.
The asus has the bonus of coming with Noctua fans, but a premium price.
There's some basic principles you are missing on cooling a cpu. Size is a matter of capacity, not performance. Performance comes from the fans, so the Rog has a slight benefit. A 240mm AIO is @ 250w, a 280mm is @ 300w and a 360mm is @ 350w. That cpu at max output can hit @ 250w, so a 240mm will see very high temps range as it's at the limit, the 360mm the lowest as the temp curve is still at @ 60%.
It's an I9-9900kf. You won't get frozen, it's too much wattage output. But the bigger coolers will be able to keep you within normal operating ranges and under throttle temps.