How strong is EPO foam.
Can it hold 1000kgs
Which is better
Carbon fibre or epp foam

Dude,
1000 Kgs? i think you need an actual Airplane for that.
Foam not helping

designing a 1000kg rc airplane made out of foam would be an interesting challenge not gonna lie.

imagine how big would it be xD

On a serious note, if you're looking for a 1000kg airplane then the material should be the least of your concern. THe first one would be getting the necessary permissions and licenses to ever take off with that thing.