"How delicious is the ice cream?"
Translation:Πόσο νόστιμο είναι το παγωτό;
AFAI understand it, Πόσο meaning „how much“ isnt correct in a word-by-word sense, but means that you should use this word when asking for a quantity – so this still makes sense because we're asking for the “degree of deliciousness”. For myself, I use the following test: can you use ”very“ on the adjective in question in a meaningful way (like ”very delicious“)? Then use πόσο, else πώς.
Every word in Greek that's more than one syllable long has an accent, regardless of whether it is used to form a question or not.
Accented single syllable words are only πώς (how), πού (where), ή (or), and the weak pronoun forms μου, σου, του etc. only when not putting an accent on them could make them look like possessive pronouns.
Pay special attention to πώς (how) and πού (where) because που = which, who, that and πως = that.