It's not just the tire. Ride quality is a function of suspension plus tires. I'd recommend you change the fork oil to a lower number if the ride is too stiff.
As to the tire you can put any width tubless 17" tire on you want, but it's going to affect the handling if it's not the stock size. The stock unit is a 150/80. That means the tire's aspect ratio is 80% of the width. So if you drop to a 120/80 the sidewall is 96mm vice the 120mm of the OEM size. That will cause the front to change rake angle affecting your steering (in this case sharpen it). It also means less flex in the sidewall so the ride quality may actually be worse. I recommend single changes. First change the fork oil and see how it rides. If it improves, then try a tire change. You can also opt for lighter brake calipers and rotors, carbon fiber wheels and start really spending the nest egg to get the unsprung weight reduced.