From my limited experience, humidors capacity are rated for small size cigars. For example, if it says 150 cigar capacity, it mean it is UP TO 150 cigars, which mean you have to use mini cigars to fit that many. If you use normal size cigars like robusto and churchil, the capacity is cut in half.
I have two desktop humidors that are rate for 200, but I cannot fit more than 100. If I remove the tray, I will be able to squeeze another 20 or so.
"a large 100 cigar hygrometer or x-large 200 cigar? "
I don't understand your question. A hygrometer is a hygrometer. There is no large or small hygrometer. They all do the same job; humidity and temp. reading.
If you meant to say humidifier, then go with beads or gel. The work best for desktop humidor.