Pense desta maneira.
Quando você pendura as cortinas do lado de fora de uma janela cortada, você escolhe um local, obtém as cortinas naquele local e usa um nível para concluir a instalação?
The answer is NO! You cannot assume the trim is perfectly level. Your trim slightly off level and then you have blinds at 1" above window on one side and 1.5" above window on the other. Your level is crooked! You simply pick a spot on the trim measure from top or bottom and do the same on the other side, install. Even if out of level it looks level to the eye.
Armários são os mesmos. É sobre o contexto, não a esquadria. Em um mundo perfeito, sim, eles devem se alinhar. No seu caso, você os monta na parede. Se houver duas paredes traseiras em cada lado, você começará com um lado e modificará o lado do último gabinete - eu fiz isso mais de algumas vezes.
O que acontecerá se você montar "perpendicular"?
Most people won't notice right away but if looking long at your cabinets they will feel things look weird and a perceptive person might be hit with a moment of squeamishness. Am I drunk or is my depth perception that off? Maybe its me but I notice these things and can notice a 2nd level floor that slopes by 2% by walking on it once. But that isn't the practical reason for installing it wall mounted. That reason is simple, it is far far easier to install the cabinets, plus you won't be relying on some super complex countertop cut that needs to be made. Note that most fabricators come in with lasers and get wall curviture/issues dealt with like that. They do not work so well with floating cabinets. That requires tagging multiple points along your front cabinets. You have to think if you start at one point, you have an overhang and then 5 feet later your counter is 2" wider? Get what I am saying about feeling drunk when looking at your fun house countertops?