1. Not sure. If you are their employee that means direct labour and that means a W-2. And you must be their employee to do TN-1, but you need to check the nitty gritty with one of the people who specialise in TN-1s on here.
2. Depends on how you structure your income. You probably won't pay less tax unless you receive substantially more income than you can spend in a year and use the income leveling technique to pay less tax.
Various situations here:
Your corp receives $100,000. You pay yourself a salary of $100,000. In this case the salary is fully deductible against corporation tax, you pay the same tax as you would if you had been paid directly, the advantage is that you get to route your money through Canada and avoid some tax hassles in the US. But you will have to do all the corporate paperwork in Canada so I'm not sure that helps much.
Your corp receives $100,000. You pay yourself a salary of say, $37,000. You have no other company expenses (you probably would but that makes it complicated to explain), so you have to pay corporation tax in Canada on $63,000, which will depend on the Province you are incorporated in. You pay personal tax on $37,000. However, because $37,000 puts you in the lowest tax bracket, the combination of that tax and the corporation tax liable will be substantially lower than personal income tax on $100,000. If you carry on paying yourself $37,000, then you can use the money in the corporation and invest it. The advantage is that once corporation tax is paid, you can choose as and when to pay yourself income and you can save a lot of money on tax. The snag here is that you have to artificially reduce your income obviously. Also if you ever move permanently to the US, you can also reduce your tax payments even more by drawing down the income from the corporation and paying even lower US income
taxes (bear in mind though you couldn't have income coming into the Canadian corporation at that point as you would no longer benefit from the CCPC exemption, which means your corporate rates would be way higher).
Another option which is best avoided is to dump all the money into a corporation and pay yourself a dividend, this saves you all the T4 guff and setting up withholding and is far less paperwork, as you just issue yourself a T5 as and when, however dividends are not deductible against corporation tax so this is not a sensible idea unless your paperwork situation is so complex that it is cheaper to do it this way than hiring an accountant.
But generally speaking if your income is say, $70,000 a year, a corporation is no advantage. Plus they can be a major headache, have a look at a T2 return and some of the schedules you have to fill out. It takes me an hour to do a T1, it took me a week (40 hours) to do a T2.
Steve.