Stainless steel guarantee stick, unless you want the food to stick to build up fond to make stock or gravy. Cast iron, imo overrated because too heavy to move and flip, too heavy to scrub and season. I dont really like it even though I switched from non stick because non stick really harmful when the coating burn off. Carbon steel for me, light and easy to use.

You can't season stainless steel, I'd love to see your seasoned stainless steel pan

Once you build up the seasoning coating, it should be fine for short time cooking, like deglazing for quick sauce. But yeah don't simmer sauces, although I do my pasta sauces in a wok because it's easier to combine pasta and sauce.

You can try normal stainless steel saucepans for sauces. I prefer saucepan or wok for pasta sauces because no splatters.

Cast iron or carbon steel doesn't need "big fire", in fact it's better to use lower heat but preheat for longer because cast iron/carbon steel is NOT uniform in heat and you need to preheat longer to even out hot and cold spot. You can use dish soap to clean iron pans as well the seasoning will not come off. Most of the time it's super easy to clean, finish cooking add a bit of water while pan is hot and everything will come off quite easily with a little bit of scrubbing.

I love my cast iron wok precisely because it's so nonstick now seasoning built up and so easy to clean, literally add water and brush with coconut brush don't need soap. I hate stainless steel woks beacuse you just can't get wok hei. And everything is sticky.