I thought ON30 was the same as HO. O scale items, but narrow gauge wheelsets and using the track gauge that HO uses. …??
So, you'd want Code 100, which would be about Code 75 in O scale, and use whichever turnouts meet your needs. Peco makes Code 83 rails, which would be closer to Code 60 in O, or light rail, not suitable for 100+ ton locomotives. Maybe slow moving, but not along curves at speed.