Thickness doesn't matter in the least. I'm not in a hive beetle zone so I cannot speak to roughness as a design consideration regards the beetle.
I build medium supers out of rough sawn fenceboards that are under thickness (5/8" - 11/16"). The roughness just gives the bees something to do when they want to polish and coat their hive. That extra propolis filling the rough means the boxes really, really attract wild swarms when used as traps. So I argue that you gaining a really efficient trap system by using rough.
I use the fence boards because they are dirt cheap on sale. If you have access to a gypo sawmill, you might be able to get even cheaper material. The standard depth of deep brood is 9 5/8 -- and modern milled 1x10 are 9 1/2 or less. I used to buy 1 x12 and rip it down, but now I use 1 x10 -- and only use deeps on the bottom where the undersize doesn't matter because the space added by the bottom board.
I cheat the length of the mediums a bit less (about 1/8) to 19 3/4", so the inner hive length dimensions are same. I use 16 1/4 as the outside width, as the extra width doesn't matter, and the bees work the outside of the 1st and 10th frame better.
I run some 8 frame deeps, and I have 4/4 board scrap added on the long sides-- this means the 8's can sit on 10-frame bottomboards, and I don't have to have special bottoms. I can also add a 8 box to the top of a 10 stack and not leave an escape gap on the sides.
As I have mentioned before, my boxes are not finger jointed, but I use #20 cabinet biscuits for the corners. Cabinet biscuits are engineered ovals that glue into special slots cut with a tool called a biscuit cutter. This has worked extremely well, and makes the construction quick. The fenceboards are redwood or incense cedar. These species don't seem to cup. Eastern cheap wood will cup, so the finger joints might be necessary.
Using a $1.69 fenceboard, and 8 biscuits (at 2.5 cents each) + 8 drywall screws to tighten, means I build a medium for well under $2.