Its all about how you handle your starter and levain. At different stages of the the ferment it’ll go from sweet to tangy. A young starter/levain will lean towards a mild taste and the more ripe it becomes the more acids are created. That’s the simple explanation. Temperature also comes into play, his much starter etc… Also you might wish to try different flours for your starter and bread. Wholegrain tends to be more tangy and bread flour less so. If you’re feeding your starter wholegrain then switch to bread flour. Feed your starter more often but if you don’t wish to be slave to your starter then just give it a few healthy feeds before baking. I can tell you now that durum flour is very mild and has a sweet flavour. A 100% durum flour bread will never be sour and even adding some percentage to your normal breads will balance the tang. And finally try the " double fed sweet levain" recipe by Ken Forkish. That’ll be a good method to follow. Don’t give up.
P.s. Ken Forkish has some great recipes however he has an eccentric way of building his starter and levain. He always builds in excess which leads to waste. So keeping the same percentages build up to how much you need for the recipe.
P.P.s. If you wish to go down the wild yeast route but don’t like the taste of tangy bread have you considered Yeast Water?