why when looking at 2 recipes one quotes 500g of T55 and 10g of yeast when another quotes 500g King Arthur AP flour and 2g of instant yeast.
Why the difference in yeast?
Less yeast leads to slower fermentation, most likely better flavour but considerably more time required. Try both and decide for yourself which way you prefer.
hours in advance which i seem to forget to do, I like to make a poolish using a pinch of yeast and letting it ferment with some of the dough flour and water, say 50 g each, on the counter for 12 hours and then feeding it again a like amount again and then using it in 24 hours to make bread. The flavor is better and the thrifty use of expensive yeast is welcome .
10g - is it fresh or instant?