You do not need an US visa in order to land at the Niagara border. I don't know anything about the "flag-poling". I just landed at Niagara on Feb 6th.
There is a bridge on the river which connects US and Canada. You can walk on that bridge, just follow the sign "pedestrian to U.S.A". When you get to the US custom, you tell the US officer that you are there for "landing", they will understand it and give you a white paper then tell you to go back.
Take that paper and walk back to Canada side, show the white paper and tell the Canadian officer you are there for "landing", then he will give you a yellow paper and tell you to go to an office on your right-hand side. That's the final place you can get everything done. Just wait for them to call your name, fill out some paperwork and that's it. Landing done!
In terms of the "in-city landing", I posted the same question a couple of weeks ago, and someone said that "in city landing" takes a long time to book an appointment. Most people go to Niagara fall since the custom opens 24 hrs a day and 7 days a week, so you can go there at anytime you want.
Hope this helps.
