Watercooling manifold.

[nzbleach]

is this a big no-no these days? will it kill flow significantly and compromise performance?

[Xilikon]

It's useless since a optimal (in terms of ease of use and performance) loop is in serie, not parallel. In theory, a parallel can perform better than serie but it's a big pita to adjust everything so all get the same flow, enough to drive anyone crazy