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?
Value isn't ever decided on the basis of fixed supply or unlimited supply, it is decided on the basis of supply and demand, if supply is high and demand is low then the price will fall and vice versa. So if you have a control over the supply then you can actually decide the prices and also control them, just like what Tether is doing right now.
Yes Crypto is definitely way more valuable than gold, gold is just an investment and you can only store gold and not do anything with it, but with Crypto you can do a lot more things than just storing it so, definitely Crypto is more valuable than gold.