Im not sure about the one you linked but ive had pretty good luck with my jincheng panda. Ive compared it to the AB27 Honda frame i have and there are only some very slight differences around the subframe area, as well the welds arnt quite as good as the Honda unit. One other issue i had with the Jinchecing frame was that the upper rear shock mounts bent from some abuse but that didnt bother me as i cut them off when i did the mono shock rear conversion.
You are correct that most of the clones are 6 volt. Lucky for me the previous owner that i bought mine from did the conversion to 12 volt. I have a friend that now has two pandas and swapped both of them out to 12 volt and its not that difficult but none the less if its something you can avoid then good.
My feeling about the clones in general is if your looking for a bike that you can leave alone and just ride the heck out of it then get a honda. If you know you already want to dump a ton into it aftermarket wise and all you plan to really keep is the frame and reg then a clone is a good start. As for me and my bike thats what ive done.
Here is my panda.
here is what it looked like when i first got it.
