I own the Mech 5 which is great! As far as which keys to use there is no best, Cherry MX reds are just used a lot for gaming.
Here is what the differences are:
Cherry MX Brown:
They have a tactical "bump" which this is best for a more silent keyboard as well as that they are most like normal keyboards. Many people don't like them for this reason, they are still mechanical but are more like normal keyboards overall.
Cherry MX Blue:
These are better for typing, not that great for gaming for what I know. My friend has one of them and they do have a tactical "click" to them. About half way down the key press is makes a nice clicking sound which helps you not bottom out the key but is sort of annoying while playing a game. Another thing you may want to know is that they have a lighter key press then the browns.
Cherry MX Black:
These are "smooth" no sounds, everything is good. Although the only way to tell if your pressing the key is if you look at the screen. These are about as hard to press as the browns, which I own one and unlike my friends lighter (the blue keys) there are better for gaming for what I tried.
Cherry MX Red:
Same as the blacks but with a lighter key press, lighter then the blues as well. These are good, although I have not tried them since I tried blue and this is lighter I see this may get annoying with accidental key presses.