Looking for a shop requirement

[OlliBe]

Good evening,
I'm currently in the phase of gathering information about which shopsysterm is suitable for what I'm looking for. So the shop in Germany is not existing yet and this is a kind of a "presales" question. In case this is posted in a wrong section feel free to move it to the right place.

I will finally sell just 3 (three) articles therefore I definetely don't need an oversized shop, although it should of course contain the basis functionality of a modern shop - like payment, responsive design...and so on.
Each of this articles is described under a seperate domain with its own installation. This is caused by distribution issues. I know it's more efford to maintain different sites for each article, but this is not really a problem for me  as I'm talking about just a few products.
Finally the user will be forward to the shopsystem (whatever it might be) in order to order the article online. One of those "articles" is kind of a service where a photo of the customer is modified in a very unique way and then printed completely individually on a very special surface. And this is my point now: during the order process the customer should be able to deliver a high resolution pic to us, preferably without any kind of compression – just the data. Sounds easy, but it's obviously not as I already asked that question on other platforms without a positive reply.
Many thanks in advance in case you managed to end up at this line of my text and for any help!
Best regards and stay negative those times

Olli