The ice giants Uranus and Neptune are often being distinguished from Saturn and Jupiter who consist mostly of hydrogen and helium, while the ice giants have more of heavier elements than hydrogen and helium. However, is there any clear distinction or is it just that gas giants who consist of more than 50% of heavier components than hydrogen and helium are considered ice giants, or something like that?
Saturn has a little bit more ices than Jupiter but still less than two per cent. Uranus and Neptune have ices in the deeper atmosphere while their upper atmosphere is hydrogen and helium too. Do planets inbetween exist that would be hard to classify whether they are ice giants or Jupiter-/Saturn-like gas giants?