The reason you read different ways of doing this is because people do it different ways to get the same results.

I don't think any of it matters as long as you don't underexpose the shadows. When you meter the main and use a reflector as fill, you probably need to get a reading of the fill side to she what your ratios are so you know how close to move the reflector.

If you use a main and a fill light you probably need to meter both and adjust the distance or the power. Since the meter has a dome on it whether you measure towards towards the light or the camera probably won't make much difference.

Another thing to remember is that when you meter the fill side and set the camera for fill, which is usually read from the face of the subject, that you may be underexposing the lower parts of the body because of fall off.

Therefore I usually set the camera at half a stop below the fill light reading or cheat by tweaking the ASA

With negatives, slight overexposure is always better than under exposure.
If you really want to test your setup, read your negs with a densitometer.