For me FFB is fine on my G27 in any car (though I haven't tried those ones you mention) with RealFeel (without Leo). You might need to adjust settings in the RealFeel.ini file in your rFactor folder. I didn't realise this at first, but you can adjust the realfeel settings for each specific car in that file. I think the RealFeel settings you need varies a lot based on what wheel you have and sometimes what car you use. But if you have a fiddle you can find a setting which works for most cars.
EDIT: The only two settings I change are: MaxForceAtSteeringRack and FFBMixerRealFeelPercent and in general I use the same setting for each car