I was wondering if there are any waterblocks which are better for direct die custom loop cooling, perhaps that direct most of the water at the center of the block?
The EKWB Velocity is good, as is Heatkiller offerings. Those are probably a couple of your best options. Koolance Blocks are also pretty solid. I don't know how the XSPC Raystorm stacks up.
Honestly all blocks these days are within a few C of each other. If you're delidding, look for a delid bracket, one of those popular OC guys sells one but I can't remember what it's called atm.
Have heard nothing but good things about them, I especially like that they don't use electrolyic nickel plating and have far better acrylic than others. I'll likely switch all my blocks to Optimus in the future when they add in D-RGB to their blocks (yeah I love RGB).
their "foundation" AM4 block is doing well on my 3950x. after having the heatkiller all copper IV and EK Velocity wb's, optimus did provide better temps. It was their mounting design that i wasnt found of (see thread at overclock.net) but block is stellar