I have just started to play Rivals mode as I get more enjoyment out of this than playing Team Adventure(in its current format). I do prefer setting times on asphalt circuits and want to able to pick my own car, as I have discovered many of the 27 available require you to use the car provided! FH3 let you pick any car in any class you wanted.
Would like any suggestions for other good ones and if anybody has a half decent lap time I would be up for having a crack at it?! 
So far I have played Lakehurst Copse Circuit(which I quite like) it’s S1 class - I have got to roughly top 150 times but will probs struggle to get much higher as I use auto trans 
I recommended going back to fh3. Rivals was my main thing to do in fh3 but in fh4 rivals is so big dissapoiment that i dont even want drive rivals.
I dont have FH3 now as I sold my xbox about a year ago and have only just bought a new one last week. I may buy it again as I did like the Rivals and multiplayer on there. I had a lap which was 106th best but out of about 1.4 million global at the time, think it was the quickest automatic time too. Was in A class with BMW M1 - which was an absolute monster on top speed and acceleration, just had to be very careful taking corners with it like though haha
If multiplayer and rivals are what you like to do then fh3 it’s million times better to you. Oh yes those 1130kw a-class cars i have really fun time with online advetures with a-class it was holden or something like how those cars goes it was absurd, i have to admit i like more fh4 in that asbect that grip tunes are mutch better and those all power tunes are almost useless.
I know but it just feels a shame having to go back to old versions to get enjoyment out of it! I still remember a few tracks from the very first Horizon on xbox 360 and they were far better than any featured in the last 3 games!
I forget the names of most of them but I remember a few brilliant ones were Gladstone Circuit, Dam and Out and some of the red rock mini circuits and the mountain climb/descend
You can try the S2 Goliath rivals. It’s on wet roads and requires quite some dedication to get a fast and clean lap in.