What length and power is best for stream trout? I fish a lot of gold medal streams so there is a large range of sizes (anywhere from tiny brookies to huge browns). Do I need a flexible or stiff rod? I use a lot of light spinners and jigs and spoons.

Understand that regardless of the size of the fish you target, it's up to the angler's ability to play the fish properly (according to tackle limits) in order to successfully land it. That being said, I've caught some large trout on UL equipment. It just takes a bit longer.

 

In your case I would probably suggest a light action spinning rod in 7' - 8' length. This should give you a decent fight with the smaller fish, yet will suffice for any larger specimens you latch onto. Any UL to light spinning reel, with a good drag, will match such a rod. Fill it with any quality 4# test mono and you're good to go. If you are well experienced in fighting larger fish on light tackle, you might even want to consider an UL rig.

Any straight tailed, minnow colored jig in the 1-4" range with the proper unpainted jighead according to conditions will outfish spinners and spoons 10-1, no joke (the gulp minnows are killer) and for line I like 6lb nanofil with fluorocarbon leaders if big browns are a possibility. I like to stick with a 6'-6'6" ultralight or light action rod, fast action so that you can stick them with a solid hookset, the fast action also helps when you need to make the jig dance like crazy and still be able to feel when a fish picks it up. Target those browns, they are awesome fish!

I use a 6'8" light Fenwick river runner, and a 6'6" loomis trout rod. If there is a lot of brush around where you fish, go with a shorter rod, if there is less brush, I would go with a longer rod. The loomis has a softer action, so I prefer that for smaller trout so that I don't pull the small jig or spinner hooks out of their mouths. I prefer the Fenwick when I am dealing with slightly larger fish, because it has a somewhat faster action so I can get a more solid hookset. I prefer shorter rods, because I can be very accurate with them, so I if I see a fish rising, I can make a cast right to that fish. There is also a lot of brush around the shorelines where I fish, so a shorter rod is more convenient. Pair it with a small spinning reel, and a thin line. I prefer braid with a fluorocarbon leader. I use 4-6 lb Berkley Fireline, with a 4-8lb Seaguar fluorocarbon leader. Hope this helps.

I use ultra light/ light rods...6'6"...even shorter.

Line...6-8lb Berkley fluorocarbon.

I think its a matter of what you feel comfortable with. That and the surroundings.

I use light power, slow action, long rods. I mostly float fish, so something in the 10' to 12' range. If I am going to cast small spinners, spoons, or Rapalas, then I'll go with something with a faster action. Any light to ultra light rod, 6 to 8' should work fine. The lighter rod compared to bigger fish, go longer. Even though I could catch trout over double digits, I still use light line - 4 to 8 lb.