I did the Delta assessment a few weeks ago and got the invite the next morning. I don't have inside info, but I don't think the Cog/reaction tests are as important as the personality questionnaire. They might be trying to drag the type-A out of you with the tests and then ask you a lot of "lesser of two evils" style questions. On the personality portion, I stuck to the middle, for the most part, and avoided anything related to anger, manipulation, solo-operator. Leaned towards "team player" answers. I spent the most time on the personality section thinking about what they were asking. The choices are all bad, but I chose personal flaws over impacting others.

An example of how bad I did on the cog/reaction tests: I thought I was still doing the pre-test practice (badly) on one of them when I discovered I was half-way through the real deal, which didn't go much better.

The BRG/RMI and ATC parts seem applicable, but the rest are "do the best you can" but don't sweat it, as far as I can tell.