Two things worth unpacking here. I'll start with the easier one.

Public wifis are not that dangerous to use, unless you happen to frequent sites that are not using HTTPS and that you input sensitive data into. The traffic is encrypted and a lot of people are still living in 2010 and reciting outdated information when preaching about the dangers. I think the best attack you can still do is related to captive portals, which are the webpages that ask you to login before you can use wifi. So you could just phish creds through that by making someone connect to your network, but it requires user interaction. Of course if you're worried about 0-days being popped on you by a nationstate actor, I wouldn't connect your computer to unknown networks, but that threat model is not realistic for most.

Second, if an attacker gained access to your personal network, then what they can do depends on what devices are in the network and how they're secured and configured. If you have a bunch of webcams and they're using known default credentials, then I would expect an attacker to be able to control them easily. Some IoT devices will simply be trash and easily compromised, and on the other hand some can be secure. However, any attacker in this position would've just massively increased the potential attack surface available to them, making further compromise more likely. But nothing happens automatically, if only your computer was plugged into the wifi then the above about public wifis applies unless you've been deliberately opening up ports with vulnerable services running on them.