iRacing is good in terms of optimization, the in-game graphics quality adjustments are great for tweaking to your desired quality/FPS targets.
A 1060 6gb would give you a decent triple 1080p experience as the game isn't particularly hard to run.
For 1440p triples ideally i'd be looking at a 2080ti, a 6700xt or a 3070 A team mate of mine runs triple 1440p with a 2070 Super and manages to get by.