I don't bother pasteurising, just pitch some wine or cider yeast and let it do its thing.

If you're going to use quinces my suggestion is to boil them down first, as if you were going to eat them. I've tried both cooked and uncooked quinces, cider from the cooked ones always tastes better.

That’s a lot of juice from a single tree. Makes me think I need to find a tree.

My Italian friend just presses his grapes and puts it in the cellar, and it turns out (after many rackings). 16 litres though, not a lot to play with. I would add Camden and commercial yeast. My preference is just to add ale yeast treat it like any beer.