The metering basically means where the light reading is taken from to determine correct exposure. Matrix takes the reading on average taking the whole frame into consideration and spot metring just takes the central point for the light reading. With spot metring you may find the sky will be overbloomed if its in the shot but this will allow what you're recording in the foreground to be correctly measure for brightness.
Have a look for GoPro Spot Metreing (Or Metering for American results) vs Matrix Metreing. It will give you a pretty clear indication on what both do.
Another tip for actually recording would be to to have a variety of clips, the same clips over and over again get boring. Even if other RC fanatics are viewing the video, they'll still find it dull if it's all just all just cars driving around. Break up the clips of the driving with sceneic shots, close up stills of the cars, film a tree for a little! It all adds to the variety. Vaterra are a new R/C company that have come about, their promotional videos are done in exactly this way -
http://www.youtube.com/watch?v=ooCTOKOml4k
http://www.youtube.com/watch?v=UdNFqb0tMb8
In my day to day job I get to film Ferrari 458's racing yet you still have to break it up with sceneic and still shots so the video doesn't get boring. Also try and cap yourself at making the vids 3mins max, we don't have a very long attention span us humans
