You have number of options, all really depends on the the layout you plan and where our accessories are going but for all you will need to take it under the mat if you want to conceal the cables.
1. You can always take it up the drivers side B Pillar and just t the side of the seat belt tensioner, and there is a pre-made hole behind which will get you in to the panel directly behind the drivers seat. make sure your cables are tied in ad don't interfere with the tensioner (fiddly but good option if your fitting 3/4 bed cupboards fridge etc)
2. Simply run the wires between the ridges under the floor, just tape them down well and makes sure they are not higher than the 9mm ridges. (very easy and least length of cableing but probably not the best installation practice longterm, may struggle when bringing the cables up into some of the panels as there are no premade routes.
3. Ceiling as you said, very easy as has remade wire ways. and least likely to damage the cables in future or installation and only problem is struggle to find natural places tor bring the cables down into the panels without running them to the rear and down and back on themselves. - it's good enough for VW to run their looms down!
Best thing is to thinks what you want where then take a few panels and see if you can visualise the best route back.