Bear in mind there's aot of rng in 2, and nnb-ups aren't exactly tied to CE the same as they are in C1 making it much harder to study properly until we can figure out some reliable anchor points - there's still a lot we don't know about how the system works that will get worked out once close to the promise 30 crimes are released, to get a clearer outlook on ched's vision
It took upwards of a decade to figure out the arson system for 1, and 2 is about 50x more complex and filled with both rng as well as many more subcrimes that provide vastly different CE and CS than 1, it'll likely take us at least that to develop a system of measurement that's close to accurate (that and the crimes released thus far are the lower to mid-tier crimes meant for the lower to mid CE-spectrum peeps long-term, so there's not a lot of point doing hard research just yet).
The working theory right now is the best CE/n is to setup skimmers in gas stations and leave them until they collect 2-3k skims per (~a year), they'll start getting found after that point, but its relatively safe overall
As for CPR increases, each role has at least one crime attached to it, and they're all affected be your overall CE, and most have some secondary stat that helps them out (mostly battle and work stats confirmed so far) - racing does help driving OC CPR but not nearly as much as crime stats do (iirc forgery is the crime there? I don't remember and don't have the list right now lol)