Good choice on the 3/4" for bench work
Ryan I'll share my experience with a similar construction method on my layout I just took down. I used 5 ply, 3/4" Luan (it's cheaper in price but just a good in performance) in 3" strips to build dominos. I choose dominos instead of the Free Mo modules. The difference, to me anyway, is the way my ends matched the next section and not a standard. This way I could do the track plan I chose and not worry about being constrained to someone else's plan. My dominos were typically 4' long and 24" or 18" wide. I tried 12" but that was too wobbly.
The intent was not to take in up and down and drag it to shows but in case I ever sold the layout or moved... it's a good thing I did it this way as I moved the layout last week. It would have worked well for this but I never had to do it.
I'm 5'10" and this is a single level pit style layout. The base is 48" from the floor. I used 1/4" CDX (just for the deck) ply as a deck to frames that foam sub roadbed sits on. I have two 2" sections of foam on top of that. That makes my track sitting just over 52" which I find a very nice height to get a good view of the trains and still be able to reach into the corner. When working on the layout, especially towards the back or corners, I found having a 3 step stool handy.
When I took the layout down I had 3 sections on my longest side together - 1@ 3' and 2@ 4' dominos for a total of 11' and all at 24" wide - I really didn't feel like braking them down further to move this section. Although the 11' was a little weldy, it was very light and very easy to tote around.
When I constructed it I did not use pocket screw but predrilled for but joints and glue. I know SPShastaRoute has used pocket screws and shared his thoughts on this thread https://forum.mrhmag.com/post/wood-what-is-better-12188818. I also have a few photos in that thread too if you want to look at the construction.
I would do the frames from cabinet grade ply again. I would not do the foam again. Here in California it is harder to find and too expensive for me to consider again - and this is my 3rd foam layout. I'm not familiar with homasote/homaboard so I can not comment on that aspect. I used cork and was happy with that
I would highly recommend a modular/domino method to anyone to consider if its right for them.
I would highly recommend 54" as a good starting height for someone to check out. I strongly suggest you do a mock up to see what works for you best. Get a 2' wide section of cardboard tape it to the wall and try it out, reach in, look at car # etc. Try a little lower, try a little higher.
Right now the 11' section is on its side (the undercarriage is visible) and very accessible but I can't say for how much longer as more boxes keep getting added. Let me know if you would like some more pictures not covered in the already mentioned thread.
I also have this thread for a bunch of photos that might help too http://s90.photobucket.com/albums/k256/ratled/Klamath%20sub%20ver%201%20last%20day/
OK, I'm a little tired from moving boxes and I'm getting to the rabble stage. I hope this helps. Let me know if you have any questions
Steve