As an editor, colorist and motion graphics artist, I of course use dual monitors. And they are 2 very different displays, but even if they were the exact same type of display you need to try and balance them as mush as you can, and that is why I own and us a datacolor Spyder X (and yes the printing is smudged and coming off on mine).
It measures both displays, has you set matching brightness, and then lets you adjust based on perception. It can be difficult if you have very different displays but is certainly worth it so your 2 displays are as close to each other as can be.
My only complaint is that having bought the device, the software is linked to my computer. And I would love to be able to take it with my to match monitors at work, especially with rental computers, but obviously they want them to buy there own, unfortunately most companies won’t bother.