Sorry for what will likely be some dumb questions...
I have my personal 2013 MacBook Pro 13" with 2560 x 1600 screen (227 PPI) as well as a work 2016 MacBook Pro 15.4" with 2880 x 1800 screen (220 PPI).
I had been using an Acer K272HUL 27" monitor with 2560 x 1440 resolution and thought it looked pretty great. But the older 1920 x 1080 monitor that my wife was using started acting flakey, so she's stolen the Acer. So I started looking into getting another monitor for either my wife or me to use, and that got me to thinking about moving up to a 4K resolution, but I'd also be happy down-sizing from the 27" to a 24" or 21.5". I'd prefer not to spend a ton, and I believe there's a Dell 24" U2415 that was once highly rated and can be had for under $350.
So those monitors, despite having a higher resolution than my MacBook displays are also still quite a bit larger physically, so the PPI would be lower than the native MacBook displays. If I'm using a 4K screen and slide the OSX slider to the far right ("More Space"), will text be smaller than what I get on my MacBooks with their display mode set to that same "More Space" setting? I'll be working very close to this monitor, so I'd like the text to be about the same size as what I get on my MacBooks, but also get more real estate for having more windows open, etc.
Coming at things from a different angle...what are the best bang-for-the-buck monitors out there? The monitor discussed in this thread seems to go for about $600, and I'd prefer to be under $400. FWIW, I just care about it as a display. I don't care about extra USB ports, USB-C charging, etc.