Hello, if you are concerned about privacy whatsoever, you should nit be using Whatsapp anyways, as even tnough the contents of the calls and conversations themselves are E2EE, Meta sells a lot of metadata which is enough to identify people most of the time.
The question of a physical adversary is complicated to answer and depends a lot on your tech and what the OS of your router is. If you are on an untrusted network, I would suggest running a VPN directly on the device of your choice.