Is this test bench compatible with both ATX and micro-ATX motherboards?

Yes, the test bench is compatible with mITX, mATX, ATX, and eATX motherboards.

What are the dimensions of the PrimoChill Praxis WetBenchSX Pro, and how much space do I need to set it up?

Length (Foot to Foot) | 338mm Width (Front to Back | 385mm (410mm w/ 2nd Optional Rad Tray) Height (w/o GPU Bracket) | 250mm

double click image to zoom in

PrimoChill's Praxis WetBenchSX Pro - Flat Edition - Powdercoated Steel Modular Open Air Computer Test Bench for Watercooling or Air Cooled Components

Quick Install-The wetbench takes mere minutes to assemble.
Easy Disconnect-The Motherboard and Radiator Bracket can easily attached and detached in seconds.
Fan Arms-Modular Fan arms giving that extra air flow when needed.
Aio and Radiator Support-Depending on the model support of up to 2 Aio's (13in. tube length) can be used and up to 4 radiators.
Unrivaled compaptibility-From reservoirs to radiators motherboards
Anti-Vibration Pads-Foot PSU and radiator anti-vibration pads are included to mitigate those annoying vibration sounds.
Open Design allowing ease of use when building-Easy to install and uninstall hardware with it's easy open design.
Length (Foot to Foot) | 338mm
Width (Front to Back | 385mm (410mm w/ 2nd Optional Rad Tray)
Height (w/o GPU Bracket) | 250mm
Motherboards: mITX / mATX / ATX / eATX
5.25 Bay: 2x 5.25in....