FFA in the 8 player games stands for Free-for-ALL, meaning no rules, shoot whatever moves in front of you, red or green and vulcjing allowed!!!
It is best to up from a base that is behind the action so you get a chance to climb to at leat 10,000 feet above ground and get your air speed up before engaging or being engaged!!!
Ki-84 is a good plane, but if you are new to combat sims i would sugest you learn on the Spit16. The Spit 16 may not be the best in any flight performance catagory, but it is above average in all catagories (acceleration, climb, speed, energy retention, turning) and is a good plane to learn advanced ACM manuvers with.
The Ki-84 likes to compress (controls lock up) in high speed dives!!!