I have all kinds of random lamps in different states of wellbeing in my collection. I have a fixture for 2 20w TL lamps with electronic driver.

Does it matter for the ballast or for the tubes, whether the lamps you put in are old and new, or do they have to be "matched" like the output tubes of a tube amp?

I also have a conventional choke ballast (230v country) sitting around for if i were to convert the fixture from electronic to inductive ballasting, if that would be significantly better.

No. It does not matter until both lamps are roughly in spec. These are not push-pull circuits like some tube amps.

I have no idea why an inductive ballast may be better than a good modern programmed start electronic ballast with a honest ballast factor.