Ive googled as hard as I can, but the naming convention of the new console has made this an unanswerable question apparently. Has anyone who bought an X transferred data and found that their back-compat 360 titles save data transferrerd too? It says it uses the cloud storage but it seems almost emulated in a way, just want confirmation before I lose all my Burnout and Red Dead shit.

No problems at all with that. You could even start playing on a 360, move the game to an original XB1 and then move on to the XB1X as long as you used the cloud storage saves on the 360. Was more or less the point of it all from the beginning, that you could bring along all your saves as long as you transferred them to the cloud from the 360.

E: Just to make extra sure about this I booted up Mass Effect, which I had only tried once on an XB1 when the back compat program was in beta, and the save from that time downloaded just fine on my XB1X now for me to potentially continue on.

that is awesome. Thanks for checking that, im excited to make the upgrade now!