Just finished the main story at level 31. I discovered the n00b way of grinding rep: doing laps + jumps around the speedway until heat 5, then hightailing it outta there with another jump while all the cops are still stuck inside. Easy escape and 100k+ rep in less than half hour
I like Payback's story better personally. It doesn't really feel like your character achieves anything here since Torres is just Mercer Mark II but oh well, not gonna lose sleep over it. I also find the last car Mercer drove to escape a bit shoehorned in (not gonna say it just in case people don't want to be spoiled). Now focusing on doing the side stories and completing all the races.
Also, I just realised that you can actually enter a race with your PR lower than the recommended number. Rohin's off road races are so much easier with rally parts, even though you're like 100 PR below the recommended
Can confirm speedcross parts are hack for drifting too
They key to getting big scores in NFS since 2015 is to get your tail sideways as much as possible. Don't care about speed/angle/duration, but just do lots of small drifts and keep the multiplier up. So it makes sense that offroad + drift parts which have the lowest grip will rack the highest scores. If you find the car is too oversteery, then using drag tires adds a bit of understeer to keep you from spinning out every turn.
BTW, does anyone know if someone leaves your crew, do they take the rep earned for the crew away with them? My crew is level 40 now but a few people have started leaving, which is very annoying.