you can whatsapp 018 685 7364 for the different between the 3 model.
however i would suggest you put on hold first if you plan to get pro+ and plus.
there is a new model evpad 3 just out few days ago.
i have sold off the first batch of evpad 3, now pending for for second batch to arrive early next week.
HDR applies to all, it make the graphic output brighter and detail more easily to see compare to without HDR.

evpad 3 can fully replace pro+ and partially replace plus
plus still have additional 16GB memory.
unless you install alot games and download movie to the box, 16GB is enuf
if you need additional storage you can consider adding memory card or usb storage

i suggest you either get evpad 2S+ if you on budget
or evpad 3. evpad 3 come with HDR ver.10
evpad 3 has a new server for VOD. i notice significance improvement on the new VOD compare to the evod ship with the previous 3 model.