What are the basic requirements and perks that come with an assignment to WHCA?

One of the things they don't tell you ahead of time is that you can be held at your duty station for up to two years while they conduct your - very thorough - background investigation.

It’s a nominative assignment and only accepts certain MOS i.e signals intelligence and commo MOSs. Very rare for other fields to get slotted there. Usually the support fields have insane rank requirements

If you have been selected, then it means you are pretty damn good. Hours will suck, but there is damn few that can say they worked for the White House, and afterwards a lot of good slots will open up.