I have not heard any of those 4 choices. But from what I read so far, those 3 Yulong dacs do all sound different, but are considered to be very good for their price.
The D200 is more on the neutral side if I remember correctly, while the DA8 is more smooth sounding. And the D18 is known for a very warm sound, comparable to a tube amp.
Since you want to check your self made mixes, the D18 is probably not suitable at all due to it's strong coloring. May the DA8 too.
You might consider some Audio GD dacs too. They also have a good value for their price and the units with the sabre 9018 chip are known for a neutral sound.
When it comes to a dac, I would always go for a neutral sounding one and let the rest of the system do the coloring.