My loaves are good but not great - where can I improve?

Hello all, just found your site and have been reading - I think I've found my people!

My loaves are good, but I would really like to push onto the next level, so they are outstanding! I think that comes in part from flavour of the loaf and improving my crust.

Been baking sourdough for about 18 months and my loaves are very reliable. I use 900g of flour (700 strong white and 200 whole wheat) 200g of starter 620g of filtered water and 20g of salt.

I mix my dough, let it sit for 30 and then over the next 6 hours do three sets of stretch and folds. Pre shape, rest for an hour, shape then in the fridge over night to bake the next day.

Given that process and formulation, what tips would you have for improving the flavour of the loaf? Could I leave it to prove for a whole day and then bake on the following morning perhaps?

Thanks for any help advice or pointers, I will upload some pics to this post shortly.