I used a standard sized 0.4mm nozzle at 0.2mm layer height for all my prints. Note, at the moment of this posting I have not personally printed the XLR mid and top. They're about to go on the printer after the next job. These take much longer to print than the RCA versions. The XLR top, for example, is estimated at 18.5 hours on my Ender 3.
The bottom can be printed with no supports. I suggest printing with 6 perimeters. This will make the tabs strong.
The middle sections need supports under the covering for the Pi. I was able print with conical supports enabled in Cura. When removing support be careful around the two pieces that divide the USB and Ethernet port.
The top is best printed with the shape oriented so that the wavy portion is on the z-axis, basically print it with the back, the side where the USB cord enters to power the Pi, on the build plate. You will need support, but again, with conical enabled in Cura the support was at a minimum and the print time minimized. Again, using 6 perimeters will have the tabs at the best possible strenth.
On my final case print I used wood PLA and printed the top rotated 90 degrees as described. This gave the top a very nice "grain" look with the wood PLA I was using. However, printing in this manner will take much, much longer and require more material for supports.
I printed my prototypes in cheap PLA. The strength provided by PLA was enough to handle removing the supports. However, due to the brittleness of the material the tabs are easier to break. I suggest using PETG if you're comfortable printing it. I was able to print a very nice case out of wood PLA. It seems to hold up pretty well as it doesn't seem to be as brittle as regular PLA. ABS or ASA would be awesome, but I suck at printing it. Perhaps you're better ;)