Is there any reason a Leopard 2838 5580kv (380 size) motor couldn't be used with a Novak Impact ESC in a Mini 8ight? I ask because the Leopard is a 4 pole and the Novak is only rated for 2 pole motors but they're talking about 1/10 scale 540 sized motors, I think. And also wondering if there's any reason the sensor system wouldn't work properly between these two?

there shouldnt be an issue. As far as i know all sensor systems work the same. unless a wire or sensor board is faulty it should work together. Brushless motors except for some, use the three wire design and run off the same outputs from the speed control. 4 pole is more demanding for power, so a 540 4 pole motor may be too much for the novak, but a 380 should do fine.

Probably will work okay, but I have seen problems with a Castle ESC used with a SkyRC/Toro motor in a mini once... only reason I bring this up is to give you an idea of what to expect in case you have a similar issue. When the Castle ESC was used, the steering would glitch really bad... plugged in the SkyRC/Toro ESC and steering was perfectly fine with the same servo and same motor.

not all sensored esc or cable are the same . not sure if this esc has the all brushless sensored motors option as novak had there own senor wire layout...might work might not