Can RGC use the executor ability to move 2 spaces if they do not attack afterwords or can you only move if you then attack?

You should be able to move and not attack, otherwise there would be some weird interactions.

Like, let's say you move up to a guy who plays slippery target and then moves away. You can't attack now, do you have to unmove?

Do as much as you can, perform the steps in order. Move the spaces, then check if you can attack. Just moving to where there is no valid target is perfectly legal.

Just like Pounce does not need to try to land somewhere the Nexu could make an attack. Mak can Disengage anyway.

Just like you can use Brutality even when you don't have two adjacent hostile figures.