I have thought that one key advantage crypto (bitcoin, litecoin, Dash, monero etc.) has over gold is that its supply level is fixed and transparent, but can this or features make crypto more valuable than gold?
This is not clear to me what do you mean by more valuable. If it considered as marketcap then we can mention the crypto as more valuable than gold. Both has demand on their on field. If we considered crypto as legalized then the demand and price will be more than now. So it can be said that it has a good potential.
it can be, but it is not at the moment, but there is also one point that one should bear in mind
gold is a store-of-value, and some crypto is also trying to play the store-of-money role, most notably BTC, so it make sense to compare market capitalization of BTC and gold, or all store-of-value crypto currencies and BTC, but does not make sense to compare crypto market capitalization with gold, since some crypto currencies are utility tokens, or have other purpose than store-of-value