Netherland Dwarfs aren't necessarily mean and nippy, but they are much more energetic and active than Polish. That energy has a tendency to be channeled into negative behavior if the rabbit is handled incorrectly. For a first time rabbit owner, I'd be more inclined to recommend Polish. As a breed, they tend to be VERY laid back and low key. Polish are generally quiet, easy-to-handle rabbits.
If you have a stronger interest in Netherland Dwarfs, don't rule them out based on that generalization, though. A reputable breeder would be able to work with you to find a rabbit with the temperament you desire.
Spaying and neutering is not necessary for either gender. It's a personal decision for you to make based on your own circumstances.
Many sources will try scare tactics about cancer rates, but the information usually presented is based on one study in a comparatively small sampling of animals. It's certainly basis for more research, but not a single defining factor on which to base your decision. As you said, there are risks with any surgery. And in many cases, rabbits can live long, happy lives unaltered.
I do recommend spaying or neutering in a multiple-rabbit household to prevent unwanted breeding. Altering can also help behaviorally with rabbits that display hormonal behaviors (biting, charging, spraying, mounting, etc.) In a single-bunny households, these are less likely to become problems.
Do you what you feel is best.
