Unless it's been changed, the points are awarded as such:
The ENY of YOUR plane / the ENY of the other guys plane = Perk Points.
This then is adjusted by the Perk Point modifier, based of arena numbers, IIRC.
Also, IIRC, if you LANDED your kills, there was a X 1.25 bonus, but not sure if that is still in effect. I do know landing gives most perk points, a successful ditch or bail will give 50-75% of points earned, bail and capture is less, getting waxed yourself ends with fewest perk points.
So, if looking to earn points;
Fly in Countries with fewer numbers, not with the horde of the day.
Choose Higher ENY planes to fly. Hunt low ENY planes to kill.
Land your kills, or at least try to ditch in friendly territory.
Instead of La-7's, Nikis, Pony-D, P-47N, Spit 14 or 16's all at ENY 5
Substitute with Ki-84 (ENY15), La-5, Pony-B, Spit9, P-38J&L, C205, P-47-D-40 (ENY20), P-47D25 (ENY22), P47D11, SpitV (ENY25), 109G2&6, P-40E (ENY30), 190A8 (ENY31), Spit 1, C202, P40B (ENY40).