The air quality and views will depend on the whims of wind and weather. It is impossible to predict in advance when and where wildfires will start, how close they will be to your hiking destination, what volume of smoke they'll put into the air and whether the wind will blow it your way.

I can tell you that smoke from a very large fire can travel hundred of miles downwind, that smoke haze will affect the views at low concentrations that will not affect your sinuses and lungs, or only very mildly affect them.

The best strategy I know of is to consult government websites that give information about wildfires. In Oregon and Washington I use http://gacc.nifc.gov/nwcc/. I am sure there are similar sites for other parts of the west. If a big fire is nearby and the wind direction is unfavorable, having a plan B is usually the best response.

Good luck!