My opinion alone.
Get hold of Sosin/Kreh's "Practical Fishing Knots II" and your answers will be readily at hand. Mine's not in front of me, but it's about $15, if I'm close. You might also look up knots in search engines here, FFSW, other board threads and Internet search values as several sites exist for theoretical info.
For now, concensus seems to be nail knot to flyline; some use braided loops, preference weighs heavily on choices.