Ok, quite a few things to clear up:
You do not restore a Reflet image using bootable media created by the Microsoft Media Creation Tool. That tool creates Windows 10 installation media. It includes some Microsoft tools for restoring a system, including a tool to restore images created by the built-in (and terrible) Windows System Image Utility. But it would not help you with Reflect images.
The way to create bootable media that can restore Reflect images is to create Rescue Media using the Rescue Media Builder wizard within Reflect itself. That will boot you into a Reflect environment, from which you can even create an image if desired, such as if you want to capture the latest data on an unbootable system before restoring over it with a known good image.
The boot menu option boots you into a Reflect Rescue environment by relying on files stored on your C partition. But since there are several scenarios where those files might not be readable or available, it should be relied upon as a convenience, NOT a substitute for "external" Rescue Media on a disc or USB flash drive.
Creating Rescue Media on the same device that stores your backups is possible, but can involve some manual effort and introduces some considerations of its own:
- As mentioned above, if your system uses UEFI booting, you'll want your Rescue Media files on a FAT32 partition. That will typically mean creating a separate, additional FAT32 partition on your disk, since people don't tend to use FAT32 partitions for entire external hard drives anymore.
- Some PCs only support booting from USB "removable storage class" devices like flash drives and not USB "fixed disk class" devices like hard drives and SSDs.
- If your Rescue Media is on a device that is physically online all the time, it might be vulnerable to an "incident", whether that's user error, a Windows bug, or a malware attack. The whole point of Rescue Media is to be available to rescue you when disaster strikes, and the way it will be most likely to be able to do that is if you keep it offline most of the time and therefore insulated from whatever might happen on your PC.
In terms of the concern around having only one USB port, after the Rescue environment completely loads, you can disconnect the Rescue Media flash drive and connect something else to that port instead. Reflect Rescue loads itself completely into system RAM, so after it's loaded, it will no longer need access to the boot media that it came from. Or yes, you can certainly use a USB hub instead.