I have a similar setup and decided to install it on my degoogled phone because I definitely wanted to use a VPN to connect to Whatsapp and my other phone is an older Android without the global VPN option.
I have it completely isolated from my main account by using Shelter from F-droid, installing Aurora store in that sandbox and then installing Whatsapp from Aurora into the work profile created by Shelter.
This way, my main contacts and media are not accessed by Whatsapp. It does its own separate thing and I have no other apps interacting with it.