So, we now each bought a 25 inch suitcase to check and an 18 inch suitcase to carry on - and still they are full (nature abhors a vacuum syndrome). And most of the electronics are carried in one backpack, since sometimes we have to check or gate-check the 18 inch suitcase.
One goal is to get all the electronics into the carry-on suitcases, but still pack the backpack in case we need to transfer the electronics to it for carry-on. So far, that has not happened.
Hints on luggage allowances: Regional airlines in Asia are particularly stingy when it comes to carry on luggage allowances. Before heading out you should check with your carriers to be sure that you will be able to take your carry on into the cabin.