When editing in multicam mode in Vegas you need to remember a few things. No good to add it before you enable multicam editing. It seems you already know that. Here’s how I do it.
After completing the multicam cut, I select a clip on the timeline, go to TOOLS > MULTICAMERA > EXPAND TO MULTIPLE TRACKS > YES.
Then I select any clip from the camera footage I want to add effects to, right click and select MEDIA FX. This will affect all clips from that camera footage and only that camera footage. That way you don’t have to do the clips one by one. And if you don’t like the look of it after rendering, repeat. Adjusting one MEDIA FX changes all the rest.
As for NEAT VIDEO, you will need to play with the adjustments, render a small portion, inspect, and try again.