That holdennut cab isn't mine, just my "inspiration". I've seen many cabs of that style in Australian arcade, so I know I like it.
I ended up sketching mine out onto paper (where that is, I don't know).
My build process was completely different. I recommend doing the sides first. Then use batten/blocking timbers to support the cross-structures that go in-between the sides. Everything ultimately hangs off the sides.
So, you need to decide some dimensions for yourself.
My first suggestion is to make it no taller, or not much taller, than yourself (or the users). Think about where the marquee will hit your eyes. This is your "maximum" (shorter is OK).
In my cab, the total height is only just over 140cm, including the built-in riser (foot) at the bottom - although this is fairly short, it is the max height for my target users. They include my wife and intermediate-age children.
Control panel is approximately 36" where it sticks out a little. This is suited to the target user too. However, mostly CP height only varies between about 36" to 42".
If I was making it purely for myself, I would make it taller/higher.
Taller people can enjoy a low CP too, but stools recommended. Vice-versa, stools also help shorter people enjoy larger cabs, so really a great equaliser and is always good to have a couple of stools handy.
So, decide what height is comfortable for you.
For good ergonomics, your elbows should be bent, but not your wrists. A CP slightly angled upwards accommodates a greater range than a flat CP, so angling your CP is a good idea. If you want somewhere to rest your beer, get a table or built in a cupholder

I don't actually recommend cup holders! They would look tacky.
You get some flexibility to adjust the height by including a riser/foot/base into the bottom. This foot is like a base, lifting the sides up (you can run T-molding 360 around the entire side), and adds stability. It also allows you built in leveling legs, wheels and a front kickplate too. I suggest this riser/foot/base should be no higher than 3-4 inches.
Then there is the width. For better or worse, my cab ended up as exactly 53.4cm wide (internal, between the in-sides). For a single player mostly, but sometimes for two (usually young or small) players. I copied from an original Gottlieb 2-player CP from a similarly-sized cab (that I happen to have in my shed of wonders - the control panel, not the rest of the cab). Seems just right.
Then there is the depth. For a CRT, biggest concern is room for the neck. This varies a lot, but many 20-21" CRTs can have neck depth (distance from corner pegs level, back towards rear of neck) of up to 40cm or more. So, don't make it too thin.
My lowboy is 65cm wide at bottom of sides, 68cm wide at widest point (from CP corner to back). Into this, and with approx 60-65 degree monitor angle, I can just BARELY fit a 21" CRT in. I've actually had to use a thinner plywood for the back door panel! Ah well, saves a few cents too.
Hope that helps, will see if I find anything better.