How can I clone my internal BOOTCAMP to a bootable USB?

I have problems with a windows game on Bootcamp that used to work fine, and now doesn't. So I tried making a bootable bootcamp on a USB. Bootcamp runs on the USB but I would say it doesn't run as well as on my mac's internal HDD. Windows tend to not respond a lot. Also, the 32bit windows game on the USB crashes from memory errors even though I use LargeAddressAware. The game does not crash on my original bootcamp and I can get the game to use over 2GB RAM and it doesn't crash. I think maybe getting my original bootcamp setup on the flash drive might fix my issue. I also want to use this USB to be able to test doing things without it messing up my original bootcamp. I have read that bootcamp can have problems from USB and it's better to clone your existing bootcamp to the USB. Using WintoUSB seems like a great option, but I have Windows 10 Pro, and you can't use WintoUSB with Windows 10 Pro. I have also read that you can create a .CDR image using Disk Utility and then convert it to an .iso; then I guess I can use Rufus maybe to burn it to the usb. But the problem is, the BOOTCAMP uses 100GB but is a 230GB partition. I have more than 100GB available on my mac, but not 230GB and it told me there's not enough space. Also, everything I try takes so long, so I want to know what will work because I'm getting nowhere when trying things myself. Can anyone suggest an easy way to clone BOOTCAMP (with Windows 10 Pro) to a USB? I have access to both Mac and Windows to do this from. Ideally I want it to clone directly so I don't have to store the 100GB or 230GB somewhere other than the USB drive.