I use the MJUC on acoustic guitar and acoustic piano. The MK 2 mode is similar to an 1176.
How to use for acoustic guitar: dial in a good amount of compression then set the mix knob to about 50%.
The "holes" in-between the sound will be filled in while the picking transients will be preserved.
I have not used it on vocal simply because the IK Black 1176 has always been my go-to for that.
I'm sure the MJUC would be an excellent vocal compressor.
It is very common to use two 1176 compressors on vocal, or an 1176 and LA-2A:
The first one set to a higher ratio and only grabbing the absolute peaks, the second one set to a lower ratio and compressing most of the time.
The MJUC is only about 30 US dollars so it is a good deal if you are on a budget (like most of us).