You only connect to stickers to change their configuration. Nearables (like other beacons) broadcast Bluetooth packets to all devices around. There is no limit how many devices can “hear” them and there should be no difference if 5 or 100 users is scanning for them.
However, when your app will detect sticker it may want to notify remote cloud server that user is physically in the shop. Performance will then depend on your server, if it will handle that many requests at the same time.