On the public wifi, the operator of that wifi can see any data you pass through their network. They can likely see what sites you visit, but probably can’t see what data you send to and from those sites, due to encryption. Unless they have an account with you, or you provide your information in clearext, they can link your data to your devices, but not to you directly, at least not from your use of the AP. They can potentially link your data to your image on their cameras, and thus your identity.

Your ISP has the same access to your data, but they also have a payment account linked to you, and they regularly cooperate with rights holders and law enforcement.

A VPN can do the same thing as an ISP: they know what sites you visit, but probably don’t know what data you are sending and receiving, and they can link it to your payment account. However, they generally do not cooperate with rights holders, and may or may not cooperate with law enforcement in their jurisdiction. While you are using a VPN, your ISP knows you are using them, but doesn’t know what you are sending back and forth, due to encryption.

If you want to remain as anonymous as possible, use a burner device with no accounts on public wifi.

If you want to avoid harassment by rights holders while you engage in piracy, a VPN is sufficient.

Well, using a mobile hotspot will tie the IP address to your phone, so probably not a great idea if your name is listed on the account. Honestly, just use a quality VPN and you’ll be fine with your home connection.