I haven’t had humidity be a problem in any LED’s I use. Granted, I’m not based in Florida or someplace that has extreme levels of humidity, but besides a large gathering of precipitation, I’ve never heard of standard humidity being a real problem with LEDs specifically, at least not any more so than many other production tools like electronic ballasts for HMIs or something akin to that.
I could see how theoretically fans might let a bit more airborne precipitation into the light, but again, never heard of that specifically being a problem in LEDs. Most suppliers either publish or would answer an inquiry as to the IP rating of their product, that should give you at least a good start on easing your mind with regards to how much weather protection it needs.
I don’t know which fixtures you’re looking at, but I’d personally only consider a handful of instruments that had a fan built in, for both audio and performance reasons. The new Litepanel Astras for instance, have a fan but in my experience the noise is pretty much imperceptible in real-world conditions. They do however, start to cut down on power and thus brightness to the light if you turn the fan off. On some other fixtures, the fan makes a sound you can definitely hear. Fans can also go wrong fairly easily and emit some type of clicking sound or something else that just might make things a bit more difficult. I much prefer units with robust metal heat-sinks. Yes, they run a bit warmer and are heavier, but if you can deal with that easily, there’s much less compromise and fewer moving parts to go bad.