Personally , coming from a similar system , i used a rx580 and vega 64 in it In racing games ie asseto corsa , project cars ,all dirts etc those GPU were bottle necked by the cpu but did give good performance in what I used them for so in part id recommend a rx 480/580 for you, however.
Less easily noticed is the fact that with a new platform (2600Xryzen) I find I am now miles ,miles better at racing , whereas i struggled in mp races before , I now stomp ass and i put it down to frame delivery time (and its latency) and the smoothness of frame delivery ,both of which has made this upgrade (whole pc platform)worthwhile Just for racing competitively.
Your choice though, i still have a crossfire rx480 pair in a fx 8350 sabertooth combo in my living room to push racing games on my 4k telly With room and pliability for my racing chair and wheel but it is not getting used anymore since the effects i notice make it now unusable ,whereas pre platform swap i would have swore it was fine.