I know this thread is old. I received my ACM91 in the last few days. I'll leave my quick impression for those thinking about getting this meter.
Since my UT61E is doesn't fit in my pocket, I need to replace my dead 4000 count Radio Shack pocket meter. I want the temperature, so I went with this one over the UT210E.
I ordered the ACM91 directly from BSIDE on AliEpxress and selected ship-from as USA. I was prepared for 2week+ wait but it came within 48 hours in an Amazon Prime package. Everything shown on the photo was there, including the not very well written user guide. LoZ voltage measurement and regular voltage measurement has the same input impedence according to the user guide, which would kind of defeat the purpose of LoZ. So I am sure that must be a typo/error in the user guide.
Compared to known reference values on my DMM Check Plus, 5.000V, 1mA current, and resisters (100ohm, 1K, 10K, 100K) are spot on or within +- 1 of last digit displayed except for AC. My 4.999V AC is measured as 4.946V to 4.957V, but frequency is spot on at 99.99Hz as my reference. For the 1mA (AC or DC), it is the last digit shown and it was 0.001A which is same as reference source.
The meter is slow - it seem to take well over a second (will measure if interested) to show my resister values. Clamp measurement of current is difficult to judge since the position and orientation all affected the value. I can easily get +-20% variation (or higher) depending on orientation. I have to do more experimentation with that and temperature measurement.