Video RGB LED lights for still macro photography?

Higher end macro flashes have modelling lights, my MT-26EX does. Generally you don't need them that much unless you are using a manual aperture lens where you cant compose wide open and you need them for focus assist. You can always have a portable light for modelling (really just for focus assist as you are not going to be really 'modelling' light on an 10mm insect live in the field.)

I have not tried them, because the biggest loss of quality in macro is down to slow light and camera shake there's literally no point, they are not going to give me enough light to shoot at f/13 (f/26 at 2x) ISO 100 and they are not going give me the quality I want because they are too slow.

The sync speed doesn't really matter, your flash at low power fires at much faster speed than shutter speed, this is also why we move the the flash nearer the subject (which also gives the benefit, you can sync at 1/125 to get some background light back in unless your subject moves too much, but really you want the light to all come from the flash. There's a balance that you need to work around.

But flashes bare are harsh yeah, which is why constructing a diffuser setup that works for you is ones the biggest part of macro photography of live subjects, you'll often see that the longer, most useful discussions on macro boards is about how to diffuse light, or more importantly reduce specular highlights, generally subject size to light source size is good meaning they are soft, they just have harsh speculars which are bad for detail as well. There are also a lot of misunderstandings and older wives tails type advice about using some household materials which tend to not be that good in that they block more light than is ideal, but obviously you need to use what works for you.

It's not easy but this is macro photography, high quality images of alive/active small insects is very demanding on the photographer.

If there were some LEDs arrays capable of firing full spectrum light as fast and as brightly as Xenon I would jump to them immediately because an array of LEDs would reduce specular a lot. But unfortunately LEDs are not quite there yet in a commercial setting, although I do keep my eye on them.

Here's some of my work using flashes, more at my flickr https://www.flickr.com/photos/aveslux/

https://flic.kr/p/2mDfC41

https://flic.kr/p/2mdvYZR