Is the 2,000W rating real RMS power?

No. 2,000 watts is the max (peak) rating. Continuous output is 200W x 2 at 4 ohms, 300W x 2 at 2 ohms, or 600W x 1 bridged at 4 ohms.

Can it run a subwoofer?

Yes, in bridged mode it delivers 600 watts RMS into one 4-ohm subwoofer. That suits a single moderate sub, not a high-power competition driver.

Does it work with 2-ohm speakers?

Yes. Each channel is rated for 300 watts RMS at 2 ohms, so 2-ohm speakers and dual-voice-coil subs wired to 2 ohms per channel are fine.

Why choose Class D over Class AB?

Class D is more efficient, runs cooler and draws less current, so it needs less space and is easier on a stock charging system. Class AB amps are larger and hotter.

What do I need to install it?

A fused power wire from the battery, a ground cable, RCA signal cables, speaker wiring and a remote turn-on lead. Check the amp's fuse rating before choosing wire gauge.