Very strange about the visa, are you not a US citizen?
Who can import personal belongings - "Settler, Former Resident, Seasonal Resident, or Beneficiary". So, no, a visitor cannot.
Many of your questions will be better answered by the Canada Border Services Agency, and unlike CIC, you can actually get a real human on the phone who is willing and able to answer questions.
http://www.cbsa-asfc.gc.ca/noncan-eng.htmlYou would be best served to wait on importing your belongings until you get your residence permit. At the time you re-enter or "land" to establish residence, you can either bring your goods with you, or submit the "goods to follow" list at that time - they will give you a form that you need when you bring your goods over the border (or if you have an agent do it, they need it to cross the border, and you need it to claim your goods at customs).
As for moving your stuff, yes, sending to Plattsburgh and driving it up is one option. Another is ABF U-Pack moving, they do cross-border moves into Canada and cost about 1/2 of other moving companies... I used them, it worked out well for me.
http://www.upack.com/