It's perfectly possible to spot a bear any time of day in the Park, especially in cooler weather, but mid-summer you are unlikely to see bears out in the heat of the day, when they tend to nap in the forest. You don't need to go hiking into the backcountry to see bears.
Bear spray and firearms are the last tools in your toolbox. They should not provide a false sense of security. It is recommended that you carry bear spray when hiking in bear country.
Just to keep things in perspective, though, bear encounters are very rare. Consider that roughly two million people visit Glacier each year, and more than one million venture into the backcountry. On average, there are only one or two non-lethal bear incidents in a given year.