If you have a 10GBase-T stream attempting to transport over a
100Base-T link, you're going to totally max out the 100Base-T. Only
expect to get 100 Mbit/s end-to-end.
Any transport system is only going to be as fast as its slowest
link.
OTOH, sending 100Base-T traffic over a 10GBase-T link will work
just fine - you'll get the full 100 Mbit/s all the way.