Hi,
I built the AstroEq mega version, for pulleys I went with 60 and 15 tooth, the 60 tooth just fits on the eq5/old cg5 mount. This gives me a 0.7 arc secs per step using 1.8 deg 16 micro steps or 0.35 arc secs per step with 0.9 deg motor.
For motor drivers I stayed well away from drv882x and the a4988 drivers (too noisy). I initially went with tmc2100 drivers at 0.6 amps very smooth and quiet, they were pricy though at £10 per driver. I have recently built a second rig and used the more advanced tmc2208 drivers, much cheaper also (use A4988 16 micro steps in astroeq, they are pin compatible with a4988 in legacy mode). I have to put my ear near the motors when slewing to check they are running they are so quiet.
For software, I use a raspberry pi 4 with Astro berry using stars/Eros. It is excellent, the polar alignment routine in ekos gets me within 1 arc min of the pole in less than 5 mins. If you also include the guiding, focusing, cam control it is amazing. Also I can program a sequence and (if it is going to be dry all night) go to bed.