i usually try to taper it some but i'm autistic. i also almost never tie the same leader again but the basic formula i follow is>40% butt>30% mid section>30% tippet
so usually i tie a 7-9 foot leader, which means the first 3-4 feet of my leader is 20%, then i'll have a length of 15, a length of 10, and sometimes a length of 6 pound test if im getting really light on the tippet end
personally if i was tasked with creating a general purpose trout leader i would do>3.5 feet of 20>18 inches of 15>24 inches of 10>24 inches of 3x tippet
that is basically a leader that i could fish as is for terrestrials and big dries, big wet flies (like #14 and bigger) and most streamers, then if i wanted to fish smaller flies i could hang lighter tippet off of it.
honestly i see a leader as a non-static thing, and it is to be modified and tweaked all through the day. maybe you see a spot that looks fishy and you want to put a dry fly through it, but it's got a lot of weird current so you want your leader to land with a lot of slack, so to fish the run you lengthen your mid section and tippet to get a better drift at the cost of a little accuracy. or you see a big fish hiding under an overhanging tree so you tighten your leader up, make it more agressive and accurate at the cost of finesse, so you slap a hopper in front of him so it looks like it fell from a tree.
but i find the leader i just described to be a happy medium between those two extremes>>1252467
usually somewhere around a 45 degree angle in my experience unless you slide the knot to the back edge of the hook eye, but you get more action letting it hang at a 45 with a loop knot.