If you're not planning to move your monitors around from place to place a lot, you might want to consider a pair of VESA mount monitor arms. You need to get monitors equipped with VESA mounts, but that's the case with most higher-end monitors. Way back before I had kids, I spent too much on an Ergotron LX arms set. They are nice because they allow me to push the monitors to any height and aspect that I want without having to deal with the limitations of the built-in stand. I can even rotate them vertically when the urge strikes to look at things taller than wide. The arms that I have cost way more than the monitors currently attached to them, though...
The dots per inch (dpi) or pixels per inch (ppi) metric is a product of the number of pixels across (or down) divided by the number of pixels in that direction. This metric is usually noted as "dot pitch" in the specifications for the device. For a given resolution, a larger screen will have larger pixels. Those 70" 4k HDTVs may have individual pixels on the order of millimeters across, for example, and an 800ppi smartphone has pixels on the order of hundredths of millimeters across.
There is one other trivial thing to watch out for that usually isn't a problem, but may affect text quality on Windows machines using ClearType: band order. At every pixel on a typical LCD screen there are three little color filters over the valves that go in the order red, green, blue. ClearType tries to use color perception and the assumed color ordering to make text look smoother than it would physically be (it's why you sometimes see weird color fringes on text when you zoom in on images). A few monitors on the market have their color filters in the order blue, green, red. As you might expect, this color ordering makes your text look awful with ClearType. There is a setting in Windows to reverse the ClearType band ordering or to not use ClearType at all that can help. I mention this solely in case you get one of those backwards monitors and it doesn't look nearly as good as you expect.