I have had several boys and girls over the years. My personal preference tends towards having male dogs, but as I have rescues every time, I wouldn't specify and would be more than happy to have another girl. Really, I tend to think it's more about the individual dog than their gender.
I am generally pro-neutering from the perspective of preventing unwanted litters and in some cases reducing the chances of escaping/wandering, but strongly believe in waiting for full growth and maturity before getting it done. That said, I don't believe in a one-size-fits-all policy for neutering, as it's not always advisable for for dogs that are fearful, as they rely on some of the hormones that will be removed by neutering for confidence and in those few individuals it can worsen or trigger fear-related aggression (I have had a dog that this happened to.) For the vast majority of dogs though, if done at the right stage (ie after growth has finished and once the dog is mature) it doesn't usually cause any problems at all.
One of my boys gained weight when neutered and subsequently lost it again, but none of the others have had any significant weight gain at all.
Without neutering all male dogs will have some degree of prostate enlargement in later life, which can be both uncomfortable and cause urinary and defecation problems. One of my dogs was neutered as an older adult, after he developed prostate problems that led to repeated urine infections and cysts in his bladder, which required lots of tests and two anaesthetics, so personally, I would always neuter at maturity to prevent putting another dog through that. Interestingly, he was the oldest dog we've ever had neutered and he was also the only one to gain weight, so it could have been more to do with his age and generally slowing down than the neutering itself.
The cancer prevention thing is a bit of a red herring, as whilst, obviously it will completely prevent testicular cancer, there is some research which suggests entire males are less likely to suffer from other types of cancer.
You can find registered dog trainers in your area on the APDT site, they should, in theory all use completely positive training methods, but you do have to be careful and it's always advisable to visit and watch a couple of classes before taking your dog along if possible. Personally I have found the IMDT trainers to be more likely to be completely force free and up to date with modern training methods.
Can't help with dog walking coats for humans, if that's what you meant, as I have a condition that means I overheat easily when walking, so can only ever wear a really lightweight raincoat at most.