1. oil, two stroke oil?? if u still running on oil pump you can use motul 510, agip speed castrol tts silkolene pro 2 etc....

2. transmission oil, can use the motul or repsol transmission, or use the 4 stroke engine oil

3.are you sure the carb is clean? the jetting is properly right? what sparkplug are you using?what is the color of the spark plug? I suspect that's due to dirty carb or wrong size of pilot jet. I don't know with the kymco, but the stock carb for nsr 150 is PE26 and PE28 for nsr 150SP.
I don't think the idle problem correlate with the rc valve but make sure the rc valve mechanism is right. on L position in low RPM and H in High position, by default it should full open (H) at round 7000RPM, but you can tune them as you want....

btw Welcome