@G-I-Jones
You can use these instructions or others you find on google.
https://kb.vmware.com/s/article/2042141
So, if the USB dies, you reload the same version of ESXi onto new USB key, keeping the storage drive in tact, set IP address and then restore the config and reboot. Boom! all done. It is that easy as I had to do it once.
I recommend backing up the config every time you make a change. I never really delved into profiles either but from what I hear, you can save those in vCenter. Once you add the server back, reload the profile, reboot and you should be good to go.
ESXi is loaded all into memory after boot up. Other than USB disk checks, nothing is stored on the USB key after the hypervisor is loaded. It mostly writes to the USB key on reboot/shutdown.
If you use a USB/SD key, you will need to create a log folder on your storage volume to save all the log files. After install, set the ScratchConfig parameter with the correct path and reboot (It is easy so don't worry).
https://kb.vmware.com/s/article/1033696
If you want to really go nuts on DR. Backup the config while it is loading, take out the USB key, use Linux (I use clonezilla) and clone the USB key. Then put the key back in the server. You should be good.