But do you also segregate the devices and networks you connect to for this identity, or can a sufficiently advanced adversary connect the dots where you link up with the rest of the internet?
No. They all go through the same ISP. And through the same initial VPN, because simultaneously using multiple VPNs would be unusual. But after that, I branch out to multiple VPN chains, and multiple Whonix instances.
Like this: https://www.ivpn.net/blog/wp-content/img/Chains.png
VPN4 is OpenVPN via Tor.