Makes resources more sparse than base game. You will need to use trains much earlier to get resources. Game will be more difficult especially with higher enemy settings.
Tweaks
Mod category: Tweaks
Small changes concerning balance, gameplay, or graphics.
RSO doesn't modify minimum yield in any way I think.
There is a chance that since that base game mechanic that increases minimum yield based on initial one worked on it. I'm not sure how it works exactly so I can't confirm that in any way.
Is rso only mod you have or there might be others that modify the oil wells?