I have done the primary in a carboy. Yes cleaning can be a PITA.
Grape berries or peach pulp don’t really work. Most yeast are “clean fermenting” but some yeast as Maurivin B foamed about as much as liquid volume. Some pulp is worse as choke cherry foamed a lot.
* a low temperature fermentation as 10C / 50F is slower and foams less
* there is no reason you can’t do your primary in two containers. I normally am fairly close to batch volume but if it needs more volume I pull some out. ,,, You won’t know how it will work until you try that combination.
* Yeast cell growth (from 1.090 to 1.050) requires oxygen. This is natural with an open top. With closed containers as a mead recipe the direction is to stir to mix in some oxygen early in the process. ,,ie ,, Do not use an air lock till after the first third of sugar (cell growth) is over. After first third using the airlock is appropriate.
* there is a technique called step fermentation. I have fermented and added more juice at day two and three or when topping off after racking.