hello all, new to electric flight,

-one plane(parkzone corsair) requires an 1800 mah, 3S, 15C, 11.1v battery. it has a 30A esc.

-second plane(Extra300 Airfoilz) requires a 1500 mah, 3S, 20C/peak discharge 30C 10 seconds, 11.1v battery. it has 35A esc.

...........sooooooo i havent bought more than 1 battery each because i am confused.
Q: are the milliamps the "gas tank"? more mAH and longer flight time?

Q: ok now, can i put a 20C battery in a 30A esc? or does it have to be 15C?

Q: can i use a 2100mAH, 20C, 3S in both of these planes, if not what do i need to do to maKE that happen?

*basically trying to buy a couple planes that i can use the same type of battery on for simplicity.
HELP! ANYONE?

-WINGMANEPTX-
KEVIN