Halogen to LED conversions aren't always "plug&play". The position of the light source in LED's can vary relative the near point source for any incandescent (Halogen, etc.) lamp. The results can be anywhere from no real change to almost impossible to aim (dead spots, and hot spots too high). Also, the fan assembly can, in some cases simply not let the lamp seat properly, or there may not be enough volume behind the reflector. Even if all of that works out, any dust seals that work with non-LED's may not work with an LED lamp.
Which isn't to say "don't do it", just don't expect to pop out the old lamp, put in the LED, and be good to go. Murphy never sleeps, he waits...
6500K is blue white, ditto for 5000K, the light doesn't really approach yellow until dropping well below 4000K.
Sad but true, quoted specs can be ...um... creative. In the case of headlight kits, claims of 110 watts(!!!) turn out to be 55 watts per lamp. Of course, lumens are doubled, too. Factor into your thinking that while the box may say H4, not all H4 LED's are the same as other LED's, or halogens.
Yes, I do have a degree from the College of Hard Knocks, School of LED Engineering... Yes, I have some wonderful spares looking for new homes...