I read with interest your questions re Puerto Montt and Lake district. We went on land tour that did the Lake crossing - middle of their summer - and nearly froze - sleet, rain the entire day. Had been nice the day before. So I would be wary of signing up for the tour ahead of time - weather could be bad and you would see NO scenery, etc.
We are taking the Val-BA cruise in Nov and will try the private guide - if weather cooperates!