JB,
You will find the Dash 8 400 different than riding in a jet. They have a slightly narrower cabin than you're probably used to, and will be more noisy, with more vibration. Depending upon where you sit, you'll have a good view of the propeller, and main landing gear operation (don't let it startle you!). The turboprops necessarily serve different routes and markets than jets - they will go places jets don't. And, they are more efficient on shorter routes.
A have flown as a passenger on nearly every kind of aircraft for half a century. I am equally relaxed on either turboprops or jets, even with the differences. I worked for deHavilland at the time that the original Dash 8 was developed, built and tested. I was amazed at the incredible strength and durability of the airframe. Since those days, that airplane has demonstrated itself to be incredibly reliable, and worthy of the routes it serves.
No one can tell you that there will not be an unpleasant event while you flying, or driving, or taking a train, or walking to the store, or stepping out of the shower, or..... It's up to you the risks you take in life, and the benefits you enjoy as a result. I can say that in all those decades, in all those types, I have never felt unsafe as a commercial air passenger. On top of that, I have also been a pilot for more than 40 years. A few of the non commercial and flight test aircraft I have flown were a little less reassuring than commercial turbo props and jets, but we're not discussing flight testing and training flying.
Put your faith in the very complex system of training and maintenance which the world's authorities impose, and go for the ride. I suggest choosing a seat more aft in the cabin, just behind the wing, it is extra strong and safe there, and a little less noise and vibration. Watch the safety briefing, and understand it. Read the briefing card, and understand it. Consider what you will actually do, if you had to exit quickly. For the few accidents, passengers who exited safely, generally did so because they were mentally prepared. Keep your mind sharp (no drugs nor booze to dull your senses/reactions).
You'll see the mainwheels vibrate with rotation and runway contact - they're suppose to. You'll see the wings flex a little - they're supposed to. Indeed, we watched the final "iron bird" destructive test of the original Dash 8 wings, after tens of thousands of hours of fatigue testing. The wingtips were pulled up hard relative to the fixed "fuselage" by immense hydraulic cylinders. The eight foot stroke of the hydraulic cylinder was not long enough to bend the wing when pulled, so it sprung back to its original shape, and the test was declared a pass far in excess of expectations. Have faith in the aviation industry, as you'd have faith in any other regulated industry. Nothing is perfect, but we really do work at being safe!