As for the number of patterns...
As many as you can come up with. There are several ways of strumming one kind of music, butr they are all based on the timing and rhythm
Another more challenging strum after you get good at the basics is when possible strum down then pick the high E, B and sometimes G strings one at a time from bottme to top. The idea hear is I think to increase versatility, switching from strums to picking can be very handy. I pick about 1/3 of the time I play usually it's just random notes but it sounds great
Anyway