Given what you wrote, it would probably make sense for you to first get a good keyless flute, and later move on to a keyed flute if you realize that you really like it and need a chromatic flute. Since you seem to be in Europe, it might be worth checking Baubet and Thompson. Both of them are based in Ireland, and make well regarded flutes at a fair price. (Thompson’s order book seems to be closed at the moment.) There are also second hand instruments that come up regularly, here or on specialized facebook groups.
As tstermitz said, the distinction between Rudall and Pratten is perhaps not so useful when it comes to modern makers. The 2 modern “Pratten” I’ve tried had smaller holes than my large hole Rudall, and felt completely different from the original Boosey Pratten I owned for a while. Some makers are also willing to make a “Pratten” with a split body if asked. Having said that, if you have medium-sized hands, it’s probably a good idea to look for a flute with small to medium-sized holes.
Finally, regarding loudness/air requirements: it’s extremely difficult to generalize because it really depends on the maker’s design (body and embouchure). I recently received a small-hole Rudall that is at least as loud as my large hole Rudall, which is plenty loud in itself, but it feels like the smaller holed flute takes less effort to get a comparable output, volume-wise. Both are excellent, but they play very differently. The point I’m trying to make is that the more flutes I play, the more I think each flute (or maker’s design) should be judged on its own merits. But for this, unfortunately, there’s no substitute to trying the flute yourself and seeing how it fits you and your musical context. Good luck!