Started with whole wheat flour, what I have found is that whole wheat flour gives more acetic acid and bitter taste upon fermentation(which is reduced by toasting), here fermentation taste is not that special, though after toasting it feels alright, with refined flour, fermentation gives a taste on its own, it feels more like yogurt and not bitter at all(except if flour/ingredients are bitter), other than fermentation flavor, it's flavor profile feels relatively simple(unlike whole wheat). I live in India(your results will likely vary), also I have found that whole wheat flour gives alcohol taste also, more noticeable at higher hydrations. For bread made for toasting purpose 10% olive oil gives better flavor than no oil at all(confirmed in case of whole wheat flour)
Also I keep dry starter retained from previous bread dough, it does not smell bad even after 3 days on the countertop, what I have found is that upper part smells pleasant but not the lower part, I think this type of starter should be aerated, so now I'm keeping it flattened like pizza.
I think I've been underbaking my loaves, today I tested internal temperature after baking at 230c(446f) in preheated dutch oven for 25 minutes, then 180c(356f) for 25 minutes free standing, internal temperature did not reach 95c(203f), previously I used some other stainless steel utensil which I did not preheat, 180c(356f) temperature time was around 35 minutes, I kept loaf in the utensil itself, bake time difference is huge, total time to reach 95c(203f) is around 25 minutes for the dutch oven part, free standing part 70 minutes.
Here's what I used(not exact values):
100g dry starter
75g olive oil
It's baked straight from refrigerator with around 6c(43f) temperature.
For refined flour I have not used more than 800g in a loaf.