WILL THE ACCOUNT BE FOLLOWED IMMEDIATELY AFTER SCANNING THE NAMETAG?

No. As mentioned above, once you scan a Nametag, you will get two options — Follow and View Profile. If you want to follow them, tap on the Follow button.

In case you already follow them, Instagram will notify you about that.

WILL CUSTOMIZING A NAMETAG AFFECT THE EXISTING ONE?

No. Your new customizations will not affect your current Nametag. If you have shared it publicly, people will still be able to follow or view your profile using them.