Let me see if I can figure/help you out on this. Ok, first, Overwatch: the default map you first see when you log in, shows you were YOU are and anyone else that's in a default session, (will show you on the map with other players, but you're not in that session), Shows other players as "Rivals". Any other players will see the same thing for you, "Rival". When you go into Navigation mode, it tracks you everywhere you go on the map. In Overwatch mode itself, you can click on your driver and use items to boost car health, nos, etc. You can also click on any other players in that session and help or hinder them with stuff. If they have Overwatch enabled on their end anyway.
Not sure what you're talking about as far as other racers/cops taking you out, setting you up, but are you talking about other actual players, or the AI racers/cops? If t's other players, then all I can say is watch were you drive, move out of the way real quick, use a pursuit tech like shockwave or electrostatic field, etc. If it's other players, are they using overwatch? If so, you can disable overwatch in your game settings so no other players can hit you with roadblocks, etc. if it's AI racers/cops, well that's just part of the game. When you start a pursuit, any AI cops will also chase that racer whether AI or Player. The AI cops will have roadblocks set up for that racer. It's the same as if AI cops were chasing you. They will set up blocks, use heli's, spikes, etc on you. Hope this clears up some of your issues there.
Cars freezing: System specs. Do you have lag, stutters, static in music, music cuts in/out, etc? This game wasn't optimized too well for PC. Depending on your system you could be experiencing slow ping times, slow load on graphics, etc. Do you see cars doing this?:
https://www.youtube.com/watch?v=RzClWsn8j-g
Other cars in game seem to "twitch" or look like they're "repeating"?
If you have a headset or a microphone connected to your computer, look for me in game and i can see what you're dealing with. Rivals does have voice chat.
Oh, also on overwatch, if another player is in overwatch, and in the same session, they can see where you are just like you can see them. It only shows "Rivals" on other players names on the "default" initial log-on map. Anyone else on that default map will only see "Rival" above yours. In overwatch, only someone in that session you're in who has overwatch can see you. Hope this helps.