Having had a similar device back in 2015 I would say performance is 100% dependant on the quality of the source voltage ie the batteries you use. If you use elcheapo LiION cells then chances are you will get poor performance.
At it’s core it is a DC-DC converter and as far as I was aware at the time on mine (looks very similar) it runs all 4 LiION cells in parallel to source the input voltage for the converter. These things will run warm if you are running at a high current and higher voltage (They were designed originally for 5V I think, might be wrong,the option to go to higher voltages was seen as a ‘useful option’) also any radio might be susceptible to RFI from such a device and common mode chokes usually can deal with any issues. To be honest I never saw issues with mine I set the output to 11V for the ATS rigs.
I used to power ATS3/ATS3B and even a KX3 (at low RF powerout).
Basically it works.