17v - because it have to be more than 15v (can it be much more than 17v)?
Yes but as Paul says get what you can, I have never seen a 17V power supply, you can't get all values.
- minimum 5W - because that's what each led-pcb is?
That is the wrong way to think about it. You need a power supply to deliver the voltage at the current you want. So if you need 75mA or even 350mA for each LED plate then you have to provide that current times the number of plates. As it is never a good idea to run a power supply at its maximum current then look for one that provides at least 20% more than this current. Remember the current rating is only what it can supply not what it will supply.
I guess the led "takes what it needs"
No the LED takes what it is given, the constant current supply gives that. What you need to do is to power the constant current supply with a power supply that will deliver that voltage and current.
Would a driver like this be appropriate if I choose to buy a driver instead of making my own?
As it stands no. This is because it will deliver 1.5A into your LED and fry it. You might be able to modify it to only give 350mA but that will take a bit of understanding and some test equipment. Look for one that delivers 350mA or less if you don't want it as bright.