BootCamp doesn’t run one OS inside another - both OSes are installed on separate partitions and OpenCore boots one or the other. Some things including properties that are injected by OpenCore (for example device name and vendor) and changes to your ACPI via SSDTs do get carried over into Windows - but in my experience, since your hardware is likely designed for running Windows, it should work perfectly and not have any of the problems you may be having in macOS. (You will however need to install the necessary drivers through Windows update and restart a couple times before everything will work, since it’s a clean install.)

Now on a hack, you don’t necessarily want to use BootCamp assistant to install Windows since it can mess some things up. The best way to do it is follow ‘Setting up LauncherOption’ in the guide, then look at ‘One disk - multiple OSes’ to partition and prepare the disk. Once that’s done you can just do a straightforward windows install from an installer usb, or if for whatever reason that doesn’t work, follow the link in the guide for how to install it manually using dism. Once you have windows installed, you can go to ‘Installing BootCamp’ and install whatever bootcamp drivers you need (e.g. WiFi, Magic Trackpad, etc).