Can these brackets be used with Renogy 100 watt compact solar panels?

yes，it can be used with Renogy 100 watt compact solar panels，which can hold up to four solar panels

Did you use any type of ground rod and wiring to ground the solar array/panels?

Yes Zach I did, I bought an 8 foot grounding rod and copper wire, can’t remember gauge of wire though. If you look it up you can find out which gauge to use. Also bought grounding screws for back of solar panels with etching washers that bite into metal frame of solar panels, for good contact. Hope my answer helps with your project.

will it work with 27" wide by 36" long by 1.4" thick solar panels ?

Mine are 27 by 59. I was able to get 4 panels on it. Yours being 36 will leave excess frame, but you can leave it or trim them down. I would guess they will work fine.