You are correct about the Yamaha mixer.
Actually, I can use just the Yamaha by itself, and would probably be ok, and will be comparable to my set-up now.
But during the time I was playing around with my set-up, and this was about 2 months ago, when I had my issue on my sound coming out only on one channel. I tried hooking up my Yamaha to my Presonus DAW (at the time), I heard noise from my recording. Looking back, it might be operator error, as I could have tried lowering my output volume from Yamaha into the DAW (that could have been why it was having the noise in the recording).
Then, A good friend, audio engineer from Los Angeles, excitedly recommended the UAD Volt 2/76 to replace my Presonus Studio 2/6.
At the time, I always was not all the way happy with the Presonus (I owned an older Presonus DAW before, and that older version was noticeably better than what I had, so I elected to buy the new UAD Volt, which has built-in compressor and vintage mic preamp.)
The Yamaha has a built-in compressor, but do not have the mic preamp.
Currently, I am using very little compression from Yamaha, and about 3 o’clock on my UAD compressor knob.
Bottomline, you are correct, I can just use the Yamaha, and I will be fine.
Currently, the only advantage I have is the UAD vintage mic pre-amp.
Because Yamaha has built-in compression and also a USB (DAW) connect-direct to a computer.
So for other folks reading, the Yamaha MG10XU is an outstanding interface for live connection from XLR instruments/mics into a computer via USB (acting as a DAW).
For my purposes, the engineering invested by UAD for compression, vintage mic preamp, and DAW quality are very good value for the price of the UAD Volt 2/76.
In my opinion, my recording sound has dramatically improved with my current set-up in comparison to my older set-up. And in the end, I am happy with my investment, which is not expensive at all.