What army composition should Quatro-Lavaloonian use?

Yeah, inferno towers are the hounds only real weakness so most TH9 bases will be relatively easy. Rage spells are always important. A clan castle with some extra minions is encouraged, but is technically optional against TH9. High level heroes are another aspect that would be quite helpful but is also relatively optional, much more so than a full CC in my opinion. To sum it up, yes that army comp will work, it mostly comes down to individual strategy, especially your use of rage spells, as well as the enemy base layout.

EDIT: I also forgot to mention that high level troops are very important. In my opinion loons are the most important, making up the core of your strategy.

I have been using 3 lavas 20 loons and 15 minions with 3-5 rage spells (th10 here). It has worked well so far.

Its important to pull the Clan Castle and try to take out the Queen before going full force if you can. You can try to pull CC with a giant and to save on spells get a loon to drop on them to kill them. Good Luck.