CBAZY 24AWG UL2464 Power Cable LED Red & Black 2 Conductors (2464-24AWG-2C- 25ft)

Q: 24awg ul2464 power cable is it stranded

Yes, both conductors are stranded.

Q: Will this work for rgb led strips? one person says it doesn't, but others say it does.

I used this wire for a 12 volt automotive application for 12 volt led off road lights and found no issues. I am not certain for it's use in household applications with 110 volt.

Q: Will the 18 Awg 3 conductor wire handle 42 watts?

It depends on the voltage being used. It also depends what kind of load you are connecting it to, and whether it is DC or AC. 18 AWG wire can carry up to 2.3 amps. If you're not sure how many amps (not watts) you need, I suggest consulting with someone familiar with estimating electrical requirements based on your specific configuration.