The Mugen is about the right size. It's not overly huge like the D15/S or one of the budget coolers. So it'll handle a respectable OC, it's seriously quiet and very well made. Definitely a solid choice. Other options in that range would be the beQuiet DarkRock 3/4, Cryorig H5 etc.
Basically liquid and air are the same thing, as far as ranges go. The small 120mm are equitable to the budget coolers like the Hyper212 evo and Cryorig H7. The big 120mm like the H80i and the 140mm aios are equitable to the H5, DR 3/4 etc. And that continues upto the 250w+ Noctua NH-D15 and the better 240/280mm aios. The only real advantage liquid has over air is displacement. Aircoolers can only be so big, so are limited to 250w range, whereas the 280mm aios can hit 350w, the 360mm can hit 450w. But if the cpu doesn't put out over 250w, then air = liquid for ability, it'll be on specific coolers and efficiency as to whether it gets slightly better temps.