Greybeard there are issues fitting the formula board in a 750D period..
the standoffs that are 'mounds' in the 750D rather than the normal 5-6mm posts obstruct the armour on the rear of the formula,
Only by a mm or two, but they still cause a slight alignment problem
I didn't want to adjust (read file a small half moon) on the armour on the back, or leave it off so I've taken the decision to mod my 750D and it now fits a treat... after all once I've decided I'm happy with the case, it's not going back, so no problem modding the stand-off mounds rather than the easier armour, just in case the Motherboard has to go back at some point...
the width of the mounds at their base, or rather 4-5mm down from the top face catches in first a couple, but once they were relieved another 3 places... i.e. as the first Mod allowed the board to straighten up, the other 3 touched, so I've modded those now too, and it lines up perfectly, and no strength issues as the pressed mounds are super sturdy.
ref the catches on the front, if they don't know what you need they call them "push Tabs", and sent me 'eventually the similar part from the 800D part number CC800D-Doorlatch.
if you're already sorted, sorry, just trying to help, as they didn't grasp what I needed to start with, I only got one in the end, but mine do still work but are damaged henc the request for parts rather than RMA a massive case, despite a couple of false starts Corsair were brilliant, and instilled a great deal of confidence, finally tipping the balance in my Power supply choice..
for the record my case had the front aluminium sheet taped in place about 3/4" too high?? bizzare QC, but otherwise undamaged so all good (not OC for the case)