A:
It might be; for example, I needed 14gb to backup the system recovery
for my Win8.1 desktop, but need 20-25gb for the Win8.1 laptops. This
is NOT for a full restore with web browsers and saved documents, only
for Win8.1. Your recovery drive backup my not work for two reasons -
one of which you mentioned already:
1) a 16GB usb actually has less storage due to software and
memory decreases that happen over time as information is copied, deleted, and
rewritten.
2) The recovery on D: only has the essential files needed to recover a
computer. When you go to back up Win8.1, it will tell you there are a
few more GBs of files that need to be copied for full on recovery in the
future.
I hope your Win8.1 only needs 14gb of space like my desktop. I'm
crossing my fingers for you.