Action on a guitar refers to how easy or difficult is it to press down the strings which of course relates to the distance that the strings are from the frets. You raise or lower the action by adjusting the bridge. If it adjusted too low, the strings will vibrate against the first fret and cause a buzzing sound. Lighter strings means that they are easier to press down and you can also position them slightly closer to the frets without buzzing. If the neck of the guitar is even slightly bowed, it can also affect the action. So in addition to bridge adjustments, truss rod adjustments may also be required. It's a delicate balance and therefore should be performed by a guitar technician. The guitar manufacturer also publishes exact specifications for the distance the strings should be from the neck. Usually a guitar tech will have access to those specs but, you probably do not. So, if you adjust it yourself, it's all done by guess work and trial and error, if a trained technician does it, they will have the proper tools and measuring devised to do it more accurately according to the specs for your specific guitar. That is another reason why purchasing a more expensive guitar with better electronics and hardware results in a guitar that is much easier to play and adjust.
Personally, I do not believe that jumbo frets will help at all for what you intend to do. As far as playing faster goes, it has a great deal to do with the technique in which you learn a song or riff in the first place. Your finger placement and usage is critical and when you initially learn any riff. You should practice it extremely slowly. Over and over again until your muscle memory has the precise intervals and movies down so well that you no longer have to concentrate on watching the strings and frets and thinking about what you are doing. Then you gradually increase the speed to a point where eventually you are playing much faster than you actually need to play. Then you slow down to the correct tempo and continue practicing. I'm talking about many hours of practice to get the precise notes, intervals, rhythm, feeling and speed down to the point where you are playing perfectly completely from subconscious memory.