If you are sure you are going to move in the next year or two I would not build an oven like you are looking for right now. The ovens you talk about are indeed build out of pieces of concrete and you are likely to be able to take them apart again and build them up on a different location but there is also a (don't know how big) chance that in the two years you might develop some small cracks (very normal with most ovens I think) and if you then try to take it apart to move it, you might brake it and destroy it. You will for sure have to destroy the stuco that you have to make around it. Thats a big waste of a lot of work.
My suggestion would be to check this forum and check out the other, much cheaper and more portable, ways some people are making very nice pizza's with. That way you can learn to make some pizza and after you have moved, you can build the oven you want. (and yes, preferable bigger, if you realy do not have the space to build +40 inch, then go ahead and make it smaller since any WFO is better than no WFO
If you are still considering getting a WFO now, then I suggest looking at "no mortar wood fired oven". It was how I build my first oven just for the fun to see if and how it worked. Ofcourse, it is square and it is leaking heat etc. but it realy works. I baked some very nice pizza's in it. Biggest advantage, it is very cheap and anyone can make one.
Still considering a round modular oven ? I do not think there is a whole lot of difference between bricks or modular. I have unfortunatly not tested it out myself side by side so can not give you hands on experience on it. To me it sounds like there will for sure be some difference, but thats the same for every modular oven out there. It depends on the concrete or wich duty firebrick etc. In the end, if you have an oven with enough thermal mass, I think you can bake a nice pizza in any oven. This forum convinced me of that. Some people have very sifisticated setups but some people use a simple grill and stome or kettle bbq and also get very nice results. How would that be possible if a wood fired brick oven would be a a lot better. Not saying it is not better, I just think it would be marginal and not a big difference. (I prefer brick by the way, just because it looks better)
Since you allready know forno bravo, there are a lot of people building ovens themselfs over there... ever considered that ?
gl on the decision making.