Zoom H4N Pro is a good start. Be sure to use a 8GB or smaller SD card to get a reasonable boot time, or if you don’ mind the slower boot time larger SD card is also supported.
Cardioid/ Omni/ Supercardiroid, etc, with different polar patterns you have do different stereo miking techniques, i.e:
a pair of omni: A-B
a pair of cardioid: A-B, XY, ORTF
cardiod with figure eigth: Mid Side
Different miking methods have its own pros and cons, I think most field recordists (including me) prefer XY and AB for ambience stuffs.