The largest part to be printed (currently) is the tower mount for the fisheye camera. This part measures 160mm x 85mm. The ATX PSU foundation part is approximately 175mm x 175mm in the X/Y, also requiring a print bed large enough to fit this foot print. This necessitates at least ~180mm x ~180mm print bed and ~90mm Z axis to accommodate.
The choice in what filament to use is largely up to you and your capabilities, however, it's highly recommended that the chosen plastic is weather resistant, UV resistant, and temperature resistant enough to endure hot summer sun.
Best: ABS - Strong and heat resistant. Needs vented enclosure to print safely and maintain temperature during printing.
Good: PET/PETG - Fairly strong and can withstand summer heat. As easy as PLA to print, once dialed in. Requires all-metal hot-end capable of extended 240-250°C or greater temps to print well.
Poor: PLA - Brittle and does not tolerate even moderate temperatures before deforming. Common and easy to print, but does not make strong parts.
Your slicer of choice may have different names for some settings.
Layer Height: 0.2mm or finer
Walls: Use a minimum of 3 lines for walls (Wall thickness depends on the filament, increasing standard 1mm to 1.5mm makes for more rigid parts and hides infill - recommended for PLA)
Bottom/Top Layers: Use at least 3 layers for top/bottom (Many parts will have screws/bolts that could crush through a single layer skin into the infill if over-tightened)
For load bearing parts such as wall/corner brackets 100% infill makes the strongest print
Use at least 20-30% infill for non-load bearing parts (Air intake, power network grommets, etc.)
Supports are not required on any parts with the exception of the fisheye tower . This part is best printed with the camera pocket (shallow side) down on the table for minimal supports.
If using ABS or PETG, supports may be required for bolt holes on some parts as these small portions have no material beneath them. If your slicer has the option, print inside walls first so that overhangs can better adhere.