It is generally a bad idea to run two motors off a single ESC. Some higher-end controllers can do it 'okay', but I'd council to use two. The biggest issue with offset thrust and linearity in boats is differences in the motors, not the ESCs. The ESCs are solid state electronics while the electric motors have lengths of wire wound around the stator. Can't speak for EDF planes, but very very few twin brushless boats run a single ESC.
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