Look at the thrust the motors make, then see how heavy the resulting plane is. The ratio of the two will give you an idea of how it will fly.
If you haven’t built anything yet then look at a similar sized design and check the all up weight. Most designers put it in the spec.
UMX size will be very tricky with a twin and you would need extremely light construction to make it work. You will probably want to make a + shaped fuselage not a box at that scale, like a park fly/indoor micro. There is probably a plan out there for Depron mini A10 which will save you frustration and time.