Of course, it's a question of rheology
Not so much "how thick" but "how strong?". The ice could be many km thick, but weak and mobile - like the ice in the earth's polecaps. There, the topography is smooth, because the ice flows, but not *flat* because there is an imbalance between ablation/melting at the icecap margins and deposition of snow/ice in the centre of the caps.
Now, On Europa, we seem to have ice everywhere, so there isn 't that large scale structure. the question is whether Europa is more or less smooth than equivalent surfaces on earth, and how to interpret those variations.
It isn't an easy question or a simple answer, but it's good to see people championing the alternative end-members.