The best wattage and whether you use temp control depend on the coil you're using. Your coil should give a range of wattages it's supposed to work at. Those ranges are usually exaggerated. To pick the best wattage:
- Check the recommendation - it's usually written on the coil.
- Set your device BELOW the bottom of the range. If the range is 30 - 60W, you might want to start at 15 - 20.
- Increase your wattage a little every few puffs.
- Stop when you like the results you're getting. That's the right setting for you with that coil. Your preferred settings might vary a bit with different juices.
Temp control may be an option depending on the coil you're using. If the coil is made of SS316L, you can use it in wattage or TC mode. If it's made of nickel (Ni200) or Titanium (Ti), you MUST use TC. If it's kanthal or something else, you can't use TC.
TC lets you limit the temperature - if the temp gets too high, the device will restrict the power to cool it down. It's a nice feature. As with the power settings, if you're using TC start at the bottom and work your way up until you're happy. I should also note that you have to pick the right setting for your coil material - SS316L, Ni200 and Ti each have their own setting. Check the manual to see how to pick the right one. You should also be able to set your wattage in Temp Mode - you'll have to check the manual to find out how.
djsvapour has you covered on the VG/PG ratios. I'd just add that the best ratio depends on the tank, coil and settings. 70/30 sounds fine for what you have.