Those are the
high RPM Scythe GTs. The more commonly available 1850 rpm Scythe GT is pretty efficient.
I don't think a bigger intake clearance would've made an improvement by a factor of 20(2 fans → 40 fans). Clearly it was done
to prove that cooling performance has a linear relation to the number of fans used for some lulz.
You're constrained by a small case with limited options. Stick with the H100 with radiator fans positioned in an intake orientation. It helps a bit by having cool outside air cooling the radiator. Custom loop is doable in the Bitfenix Prodigy but it has to be with custom parts instead of XSPC kits(doesn't come with single bay reservoirs).
I know you mentioned that cost isn't an issue but you'll have to justify spending that much to gain a marginal improvement in FSX. The H100 should be capable of 4.5-4.7GHz. Will there be that much of a difference going from 4.5GHz to 4.9GHz in FSX?