Nothing is wrong with the older SF750, its just that it doesnt have support for current 12VH (however its spelled) GPU power.
You'd have to order a set of cables (Type 4) seperately from Corsair.
Other options include: The new released SF850 and SF1000 (beware: there are also SFX-L units; thats NOT them).
If you want go for a struggle, because SFX-L, take the Asus ROG Loki (starts at 750W I think) or the Fractal Design Ion SFX 650. Both are great 
Other PSUs that are really good, but have less than nice cables: Silverstone 850R, SeaSonic Focus SGX / SPX.
Phanteks might be another option, they are usually built by SeaSonic, so basically for 20 - 30 Euro / USD less you get the same as the already mentioned models, but with a different branding
Cooler Master + Lian Li are a worse option, because of their noise levels.
FSP Dagger Pro is ... abysmal. The PSU itself might be ok, but the cables are - disgusting. Like they took the rest of the scraps they had sitting around from some failed other project and shoddily fumbled them together. Yeah, THAT bad. I get stomach ulcers just by looking at them.
You should really look into the official case thread, where Don Dan, the creator of the case, communicates, plus other people.
A lot of people posted about it in said thread, you can just use the forum search to see if one of the AIOs you intend to use is already mentioned there.
But for a guideline:
Found at: https://smallformfactor.net/forum/threads/lian-li-dan-a4-h2o.16201/page-46#post-284324
CPU block max height is 55 mm, too.
There is a sheet in the SFF PC Master List which shows most of the currently available AIO CPU block and radiator dimensions, so thats another good guideline. That one is sortable and filterable by different sizes etc, too.
For comparison, regular radiator thickness tends to be 27 mm, so with the 120 mm fan standard size of 25 mm you'd be at 52 mm overall height. Generally speaking, thin radiator + thick / regular fan is better than thick radio + slim fan, so you could eg. go for a Silverstone Vida 240 + T30s for max performance, etc.
From my building experience, whats going to fit:
- Thermalright Frozen Edge 240 - I just finished my build with it THIS VERY MORNING (ordered via Amazon)
- Silverstone Vida 240 - built in the S396 mod, which has similar dimensions (and thus, tight spaces) as the A4-H2O
- be quiet Silent Loop 2 240 - the 280 CPU block fits, and that one is the same dimensions across the whole SL 2 series, so the 240 should fit with no issues whatsoever
