Of coolant needed after we flush the system? I've never had to do so until now(lower radiator hose sprung a leak, green going everywhere). I know Dexcool is what our cars like but just wasn't sure on the amount since this is a first for me and as for the drain plug I've heard they like to be stubborn. Would just undoing the hose be sufficient to drain? 🤔

There will still be a good bit of old coolant in the block if you don't remove the drain plugs. I've never had a problem getting them out.
I don't know what the capacity is.