I don't know about this one. The only thing I can relay to you is that the ES100 does have a built-in mic, but its main purpose is to allow you to hear ambient noise.
I don't know if it has any problems with some codecs, but it handles a bunch of them. You can lookup all the codecs they support on their website. From my iPhone app, it allows me to choose between: SBC, LDAC, AAC, aptX, aptX HD.
Yeah, I think a Bluetooth DAC gives you more flexibility so long as you don't need the convenience of true wireless where you have no wires at all. I got it so I could wear my headphones wirelessly and also so I could play music through my bookshelf speakers wirelessly.
The ES100 is an amazingly capable budget DAC. I didn't expect the sound to be so good at an under $100 price point. I got it primarily for the wireless capabilities. The only negative I can say about it is that it's not a tactile device. It's really hard to control unless you're looking at it. It also feels flimsy. I haven't heard of any problems of it breaking down, but it's not something you can toss around.