Our Packet Filter Driver (LWF) is still relatively new, so the current best practices still apply when dealing with other client applications: https://help.zscaler.com/zia/best-practices-zscaler-app-and-vpn-client-interoperability though, you should see much better VPN interop with the LWF driver.
We have a lot of environments running the new driver and progress is going well. Regarding upgrades, in 1.4 you can now enable and disable the driver from the mobile admin console, instead of using the installation parameter. So for upgrading or testing this for 1.4 and above, I’d recommend creating a small group of users, and assigning a specific forwarding profile to it. Then you can test changing between the different driver types without impacting the broader fleet.