is rinsing salt water back of my gum after brushing teeth any good/bad? saw tiktok said spit not rinse after brush but how i get all the tooth paste out

also what is the correct way to brush teeth? my dentist told me to focus circular motion between the gap up down including the gum inside outside and top of the teeth. but i have been taught since kid to brush the surface of teeth not really the gap. so which one is correct way you have been taught to brush teeth? i do feel cleaner with what my dentist suggested less thing stuck.

also is yellowish teeth indicate bad teeth? i brush and rinse salt water twice per day yellowish mean what for the health of teeth