Whether it's winter or summer activities then Telluride is your place. We've spent significant time in Telluride during both seasons and while we're obsessed with the Ski Resort we think Telluride has more to offer during the warmer seasons.
Lodging is incredibly expensive in Telluride so we recommend camping up at Alta Lakes campground (https://www.fs.usda.gov/recarea/gmug/recarea/?recid=34056).
Ophir pass is incredible in a 4x4 but careful, extremely rocky and requires high-clearance, not necessarily 4WD. We started from the center of Telluride and took "Last Dollar 4x4" to Highway 62, west to "Ridgeway" then south on 550, "Million Dollar Highway (MDH)" through Ouray (stopped at the local saloon, then continue on the MDH to where "Ophir's Pass" starts.
Trip took about 4.5 hours but was well worth it and we weren't in any rush.
Our favorite activity was the downhill mountain biking at the Ski Resort (lifts are FREE!). You can't go wrong with any of the trails or park.