I had experience with all of those and had Dnepr for a while since I originally from Kiev, Ukraine and started riding there.
I mean - I had real Dnepr, back in Ukraine. Not those polished and re-assembled equivalents exported from Ukraine.
In a word: stay away from Dnepr if your objective is to get somewhere.
I can probably add 2 pages to list below of what can and will happen to Dnepr. Not what "can happen", but what "will happen".
Jawa - there is different models, the pre-latest "12 volt" model was generally OK, but it needs to be set up accurately and thou it was not bad I won't take it to really long distance.
Izh - loads of lemons but also loads of good bikes. Planeta is kinda OK, but cc does not help it's performance to say least. Jupiter - you totally right, it is way overengineered
Out of those bikes I definitely would chose Minsk for reliability and repairability. But honestly it is 60 mph bike if all works OK.
Also there was (long time ago) Izh called Planeta Sport. Early versions of that bike were engineered with heavy participation of Yamaha, even some parts on it were Yamaha parts. It was mad 2 stroke light and fast bike.
Was not 100% easy to set up right, but it went like stink. If you find that one you can really have some fun on it.
Also, if you get lucky you may find older machine called k-750
This is predecessor to Dnepr. This is not fast, not new bike but by God it worked when Dnepr was long dead. Reliability was excellent, only problems with mechanical ignition interruptor were easily solved by replacing it with tractor item
It's pretty too in "oldtimer" style. Saying all that - if you can get yourself Japanese bike and you will be thousand times better off than any of those.