The best answer is not one resolution
The best answer is all resolutions
Modern games don't have the option to change quality and resolution for nothing now do they?
So make the graphics on highest quality and then downscale
Though positioning of sprites might be tricky but I think construct is able to make this fine adjustments
The only real problem here would be aspect ratio but that doesn't have any workarounds to begin with and only on games that are non scrolling so you could either cut, make backgrounds with different aspect ratio AND perspective or you could even scroll it