Router or Iphone internet sharing security

Hello

When connecting a laptop to the internet via a normal router with normal / default firewall or via Iphone internet sharing.

How much more protection does the router give?

Does it all depend on the user activities when online?

Connecting to the internet via Iphone internet sharing, does is make the system more vulnerable to attacks?

I don’t know, how many random attacks occurs without the user doing anything – just by having internet.

The laptop has its own default Defender firewall enabled aswell.

Thank you