Can't find a way to check range of an aircraft when applying a new seating config to an aircraft in UM/buying from factory... nor does that info available in configuration menu... where can i check such info before owning the aircraft? the accuracy of info in aircraft type page popup is only accurate to 100nm...
Nope, there is no way of knowing the range exactly unless you own one of the aircraft. You can only estimate it with the pop up tool.
Payload range chart on the aircraft info page should get you close...