Just finished the Cheetah Camo for SMGs and, as one of the oldest players around, looked to strategy rather than speed. To get triple kills you need not only speed but three willing close targets in what? maybe 2 seconds. So here are my spots:
Neptune: Bunker B MG operators on offense. On defense same bunker but on the stairs up from the junction.
Intercept: Rush to back radio room on offense. On defense final stand from MG nest side or in box car.
Breakout: headquarters main room. Defense final stand from church.
Griffin: none good on offense. On defense from the A side of B tank at start; 4 good spots behind cover in last segment.
Best Load out for my PPSH-41 was in Infantry (4 attachments): Grip; large magazine; rifling; FMG. This seemed to give the best combination since it is necessary to aim at a distance at times to get #3 and the effectiveness of the SMGs falls off quickly.
Spawning with BR and SMG/AR makes sense. People can have a choice of they want to use. Everyone wins.