There's just no point in installing a triple 120mm setup in that case unless it involves a radiator. The bottom-most fan will blow the vast majority of its air onto the HDD cage and the PSU cables. You won't notice any CPU/GPU temperature improvement whatsoever compared to a dual 140mm setup
The most natural position for dual front 140mm fans is the lowest position in both slots, which has one fan blowing air onto the GPU and the area right below it, and one fan blowing air straight onto the CPU and VRMs.
Not a Meshify, but the Define C that my secondary rig is in. It's the same frame really, just a different front and I/O panel.
I brightened the picture but the bottom front corner is still quite dark. That bottom fan is 1mm above the PSU shroud.
Perhaps this shows it better :