

You can always mock some stuff up and try it out in PrusaSlicer to see how long it thinks it’ll take?
Wall thickness potentially depends on the size of the object? I guess 2mm would the the starting point, fill one with soil, see how sturdy it feels. Complexity for 3D printing is “free”, kinda. A lot of the best container designs incorporate ribs to strengthen them without using up too much material. Given that the joins are the weak part, you’d potentially want that a lot thicker.
You also want to look at “vase mode”. Some of the fastest printing objects you can get on a 3D printer are where you design around the constraints of vase mode and then you can use a fat nozzle with thick layers to print really fast.
You can always print plumbing instead of using PVC pipes? I’ve definitely seen self-watering pots such that they just have a pipe incorporated into the design such that it just sticks up along the corner. So, worse case, each module has a watering port. If you want to get fancy, you could make a manifold such that a single pipe sticks up in the middle and fills 4 reservoirs, although the fancier the plumbing the more likely you are to have one of them get dried out faster unless your filling routine tops them off.
Taking a step back, what they’ve kinda done is taken wattle and daub (but not really) and worked it to industrial standards. And wattle and daub got used in all kinds of ways all over the world.
Obv wattle and daub to structural standards and firecode and such so that your building can meet modern specifications is actually quite a handy thing? But yeah there’s an overall myopia to steampunk-leaning researchers to focus on a singular feedstock instead of working to create a spectrum of materials based on local availability.