I do this stuff quite often for my plastic aircraft modelling. As I build WhatIf models, those that the real world manufacturers never actually got around to building,

I often need to print new decals for them, thus developing my home printing skills.
As JohnG suggests, there are many suppliers of decal paper for both types of printers, and with both clear and white backgrounds. The problem is determining the wheat from the chaff as some papers are miles better than others, and finding out which is which can be expensive and frustrating. One thing you do need is a good varnish for the decals if you use an inkjet printer as the inks are almost always water soluble, NOT a good move when you have to soak them in water to get them off the backing paper! I believe varnish
isn't needed with laser printed decals, but as I've never used one I can't say that with 100% authority.
I've always used 'Keen Crystal Clear' varnish for this and usually had no problems with it, but you do need 3-4 coats to fully 'proof' the decal. It's not easy to find in the UK as Keen have no official UK supplier, but various folk sell it on ebay still.