APFS encryption applies to individual volumes and not to entire containers. (Even if you create a new APFS container and format it as Encrypted, that will only apply to the first volume in the container.) In addition, the sensitive data volume could grow and shrink as it needs along with your startup volume, allowing (almost) the entire space of your SSD to be available to either volume.https://discussions.apple.com/thread/8335752
For most casual browsing, email and so on, I have top notch firewall and anti virus and then public internet is OK.
When in my own country, I use my HUAWEI Internet stick as it is much more secure than public Wi-Fi.
Be sure to Guest NIC profile and NOT Private. This will be automatic in Windows 10.