Alright, update:
Footsteps are BETTER with "Boost Low" audio. They may have fixed something as well in the last few days. Most noticeably in Gulag I can actually hear which way people run. Definitely helps. Still have trouble with Z axis sounds in houses though, but a lot of games (Apex, PUBG) have those problems to this day in certain scenarios. In terms of guns you just want something with a big fucking clip and decent ADS speed. I've taken after Summit's setup and started running MP7. It goes from 40-60 round mag eventually and it has amazing hipfire. If you can hit headshots with it (I'm noootttt quite there yet) you can probably take 3 people out in one clip, even at a good range. The ADS speed with the right attachments is super fast. You can even get one that improves sprint to aim speed which is HUGE. I just run SMG/Sniper but for 3's you honestly want some one running with an RPG. Trucks/Cars are just a huge hassle mid-late game because there's not an easy way to kill them besides explosives and RPG with 7 rockets is a good choice. Also thread them through windows at campers is pretty good for initiating rushes.
Only like 3 wins now, maybe 4, in about 125 games. Most BR's I'm at about 5-8% win rate (PUBG, Apex, etc) so I'm still a bit behind but I think if you just try and run and gun with the right setup and stay THE FUCK AWAY FROM ROOFTOPS you'll do a lot better.
Fuck trucks: