My incoming RatRig is 39 inches tall by 33 inches wide by 33 inches deep. Weight? I have no idea other than Heavy.

Kind of have my mind set on a Rockler steel work stand with 2 layers of 3/4" plywood for top.

Going with a 36x36 table surface.

Table height options are 16", 28, and 32"

My thoughts are to go with 16" Gives good access to the top. I can sit in desk chair and work on anything from the front below the top without bending down.
Also should be more rigid than the taller heights. Will build a lower shelf fastened to frame as well.

If I go much taller then I am standing up to work on printer and have trouble accessing the top. I am 6-2 so being almost eye level with the top.
Printer spool is inside the printer at the bottom.

What height would you go with and why?

I don't know what height to recommend. Use what works best for your plans.

But, before you commit to a stand, look at designing and building a custom stand using 80/20 brand custom aluminum extrusions and components, specifically the 15 series components. Design it to what ever height and size you want. Just do a thorough take-off and email your take off to 80/20 for quaote. I used their black 15 series components and some Oak shelving to build a really nice Stand for stereo equipment.

80/20 brand aluminum components

Yeah I looked into the 80/20 stuff and even have a design from RatRig for a stand and it is 2-3 times as much money.

Don't get me wrong I have worked with 80/20 stuff for years and love it. It is just too much money for a stand.

The legs on the Rockler Work stand are 10 gauge and the rest of the steel is 14 gauge.

I will be putting on leveling casters so I can move it or get to the electronics enclosure on the back.

All of my work benches are 2x6 and plywood.

I don't know what all tools you have, but you can do alot with just a circular saw, speed square, and a couple of clamps.

Height really just depends on what it's being used for.  Assembling a 3d printer, yeah, I'd want to sit.

I'd make a top sized for the printer footprint plus a margin, with a beefy 2x6 frame, then throw a braced 4x4 post under each corner.   Later, pull the posts and turn it into a chest of drawers for parts, accessories, filament, etc

Our qidi xmax 3 is 24" tall and sits on a 29" desk. That's about right for maintenance and normal tasks.
I reach through the top and front for a nozzle change.

Yes I agree. With your setup you are at 53 to the top and with my setup I will be somewhere around 55-57, with 16 inch tall legs, depending on what I use for a top. I can get a 3/4" thick 4'x8' sheet of sanded red oak plywood at my local Lowes for about $90 a sheet. That would give me two 3'x3' sheets plus enough material to wrap the sides and back below the top for bracing the frame.

Plus it would be great for building the printer on. Once the printer frame was constructed I could then rotate the whole table and printer. This would be a big help once the printer gets too heavy to mover by itself.

I have seen a video of a guy that built one of these printers on a lazy Susan style table. It made the whole job easier. Wasn't great for printing on though. That's why I have chosen leveling casters.

My actual work bench is built similar. I build a frame with 4x4 legs boxed with 2x4, My carpenter skills lack my mechanical skills so I used metal brackets to screw everything together. 2 layers of 3/4" plywood for top. I then found in the discounted countertops a matching pair of corner counters that had minor damage. So workbench ended up being a nice corner workbench. My only complaint with the setup is my office chair will not roll up under the bench because the 2x4 on edge hits the chair arms. If I could have eliminated the front 2x4 it would have turned out better.