Since there are a few genres of beats on there I will probably never use. If I delete those drum kits/tracks would it allow me more size on card to build longer drum tracks on the remaining drums that I do use?
No, there is more than enough space even on the shipped SD card - it can hold at about 5 more shipped default contents.
There is only one really feasible limit of 500 MIDI notes per one pattern. Though, you can have up at about 30 different patterns in a song. Navigating between them would not be as easy as one may wish, though. The current firmware only allows you to transition forward to the next pattern in a song when you hold the main pedal.
i Just went and got a 32gb sd card the drum kits load faster and there so much space