There are no FB-specific benefits for travel on KE. You are treated exactly the same as any other Skyteam Elite Plus members.

There are no FB-specific benefits for travel on DL other than a being ranked just above all other Skyteam Elite Plus members in upgrade priority - but you are ranked behind all of Delta's own elites, all of Aeromexico's elites, and probably all of VS's elites. If you want priority for upgrades on DL, you really should look at Skymiles, not Flying Blue.