I know a couple guys who use the tapered knotless leaders, but I am not a fan.
I use a maxima leader most times, 90%, and tie them by hand, riverside, as I need them. I start usually with 12 or 15lb test on a salmon set up, and taper to 8 or sometimes 6lb depending on water level. Low water, I use an extra long leader approximately 18' with extra long tippet, 4 or 6lb.
Higher more decent water, I use about a 12-14' leader with 8 or 10lb tippet. Usually 8 lb is as big as I go, but 10lb tippet is ok on high water for strength in the big flow.
I use about the same length pieces for the butt section say 3' of 12lb butt, 3' of 10lb, then 3' of 8, then a tippet of aproximately 6' of 6lb. When it starts to get short, I just add more, for the first while as long as the rest of the leader is knot free, I will add right on the 6lb.
It doesn't have to be a formula so strict, and the main thing is to be able to craft up a strong, decent casting leader, that is unobtrusive to the fish you are after, in under 5 minutes, riverside. It'll turn over just fine if you can cast at all, and adjust the lengths a bit to get it right. The other varibles will cause more grief than your leader, fly size, and wind, as well as position in the water in relation to what's behind you and where you need to put your fly. There is no exact science, because conditions can change rapidly and endlessly, so adaptability is the key. Increase your casting skill, and you will be ahead of the game. One of the absolute best casters I know uses straight 10 lb mono off of a nail knot to his fly line, and he does well catching salmon. As always, everything is relative.....
Whatever you use for a leader, get so you can get one that is strong tied on quickly on the river, and get back to catching fish.