Tight clothes can actually decrease your supply. In older times they would wrap a tight cloth around their chest to restrict flow and dry up. Loose is best
Tighter clothing stops your boobs from leaking during letdowns, so your milk gets stuck and will make you fuller. This actually signals to your body that it has an oversupply and to produce less milk moving forward
Tighter tops can limit milk flow which can lead to clogs :/ should never wear anything too restricting