Using two network adapters on the same Windows 10 machine

There are multiple elements in how an OS decides what to do. The simplest overview is that if there are multiple devices a packet can be sent via the OS is programmed with an order of preference based on the (theoretical not actual tested for this pc) expected performance of the Interface. This typically prefers ethernet over wifi, and the first device in its class the OS knows (eg the first ethernet adaptor if you have multiple identical ones).

The OS implements these decisions by modifying the routing table. An ordered list of routes is set up, with all appropriate entries for all devices, along with priorities. When a packet is sent it is sent using the first route that matches.

At the top of the lists are direct routes to connected systems. (These are calculated based on ip address and netmask)

Next come specific routes to other devices through a gateway/router - these also are broken up using netmasks. They are not typically present on an end user PC unless a vpn to is being used. Netmasks themselves have an order - with more specific netmasks (ie one grouping fewer ips) is preferred.

After this comes the "default gateway" which is where unknown packets go. (in reality this is just a special case of the previous rule with a netmask catching everything).

Devices like VPNs and hardware that balances traffic is typically done by creating a virtual device that follows the above rules.

If you have 2 interfaces and want to control which interface may be appropriate way is to associate different networks to the devices - eg 192.168.x.x to your normal connections and 10.0.0.x to the devices which connect to your Pi. (although there are more complex solutions which can work better - but which need a good understanding if netmasks and your specific requirements)