I can tell you what I've tried so far,
1 - Createx Wiked color detail (these only work well)
2 - Pen color (already diluted although it is best to dilute them a little more to have fine lines)
3 - Liquitex ink (ARE READY AND ARE GREAT, fine lines and precise.
Remember, to prevent the color from drying in the tip, you have to buy the slowing of createx and add it to whatever color acrylic you decide to buy (it is a thinner which slowing the drying).
I now use synthetic colors and you can not understand the huge difference between acrylic and synthetic else.
With synthetic you can do stretches under the tenth of a millimeter and the color quality is unsurpassed.
Now I'm working on a new work made with synthetic colors and the result is stunning.