A bit about the hike and terrain. The Pioneer Ridge Trail climbs about 5000 feet (1500 meters) in about 4.5 miles (7.2 km). It is a very long, steep, and challenging day hike. For obvious reasons, most hikers typically want to go as light as possible. The upper part of the mountain is alpine tundra, and relatively easy to search. The lower part of the mountain is dense brush, devils club, and heavy tree cover. Searching the lower densely vegetated areas by aircraft is not at all effective. Searching on the ground in that terrain is very challenging.

While a small signal panel would be easier to spot than a person wearing dark clothing, it would still be very tough to see from the air under the tree cover.

I am aware of no such tests. I am skeptical that a small smoke device would help much under that vegetation cover. I think the small amount of smoke from that sort of device would be so dissipated by the time it got above the trees that it would be very hard to see from the air. A military smoke grenade would have worked (they were effective even in the Vietnam jungle), but hikers are unlikely to have or carry a military smoke grenade.

Note that even an InReach might have problems getting a signal out through the woods, as their transmitter is very low power (I think 1.6 watts). A PLB has a much more powerful transmitter (5 watts as I recall), and would probably be the best choice in that situation.