If you’re driving, the Peace Bridge in Buffalo usually has the shortest wait times. Rainbow Bridge is usually the worst.
There are a couple other very less well know bridges to the Canadian side. IIRC, the Lewiston-Queenston Bridge is one. The Rainbow Bridge is another.
There is a tiny little bridge that I found once that the locals use that hardly anyone knows about. It’s north of the Rainbow Bridge and I don’t recall the name or if it’s even in use any more. The customs agent was surprised that I found it but it had no wait time.
Niagara Falls Bridge Commission
http://www.niagarafallsbridges.com/index.php/services/traffic-conditions
Another option is to park on the American side and walk across the Rainbow Bridge. A lot of people walk the bridge, but it’s quite a hike so if someone has trouble walking, they’re better off driving and trying to find a spot on the Canadian side to park.
Also the Butterfly Garden somewhat north of the Falls on the Canadian side is wonderful.