Will more heat give more flavour or just to a certain point??
It depends on the juice, I think, but yes, *to a point* -- I finally got to 10-ish watts because it really does make my strawberry & cream *pop* if I goose the power just a bit, but since I like a very tight draw, I can't go nuts or it gets too hot for my lips, and if I went even further, it would burn the wick.
It's really a very careful balancing act between heat (hi-wattage or lo-resistance), airflow, and type/viscosity of your ejuice. Each ejuice will be different in what temp suits it best, and differences in the viscosity (depending on the PG/VG ratio) will have an effect on how well it wicks; very thick juice may need a lower temp so that it doesn't "burn up" faster than it can be wicked-up; lower temp could be a matter of lower watts or higher resistance, or simply greater airflow.
Andria