Honestly, most people rush into this and end up with a setup that looks pretty bad because they ignore pixel density. Unfortunately, I've seen way too many setups where the vertical screen just doesn't match the main display at all, leading to blurry text and weird scaling issues that are just not as good as expected. If youre running a high-end ultrawide, you really need to be careful about the resolution mismatch. Quick question tho, what is the exact resolution of your 34 inch? If you have a 1440p ultrawide and pair it with a 1080p vertical, the cursor jump and font size differences are gonna be super distracting. Also, please avoid TN panels for vertical orientation at all costs. The viewing angles are usually trash once you rotate them 90 degrees, and youll end up with one side of the screen looking darker than the other... its a common mistake that totally ruins the experience. Stick to IPS or you're gonna have a bad time.

24 inch vertical is highly recommended!