I second all other fellow users’ comments regarding the limited 2K resolution of the 2011 TB Display, and I’ll also add this tidbit from my area of expertise, typography.
Since Apple started introducing Retina-class screens, first in 2011 with the iPhone 4, and later in 2013, with the 15’’ Retina MacBook Pro, they’ve been moving away from a very important text-rendering technology for conventional LCD (as in @1x, or non-Retina, ≈110 ppi) screens (which Retina screens made obsolete and effectively unnecessary): sub-pixel rendering anti-aliasing.
By using pixels with specific colours (instead of pure grays/opacity levels of a specific colour) at the edges of stems and curves in letters, so that their respective red, green and blue sub-pixel components light up in specific patterns according to their relative positions, this technology effectively triples the available resolution on the x-axis for text rendering.
Here’s the thing: the first versions of macOS which started deprecating this technology still allowed users to set an invisible preference list flag to reactivate it, then during a transitional phase it was still possible to do so but only parts of the UI still used APIs which were compatible with it, and the latest ones (including all versions compatible with M1 Macs, and the Studio obviously comes pre-installed with the latest macOS 12.3 build) lost this functionality altogether.
So effectively text will now be rendered only in dumb gradations of whatever its colour is, and look much worse on your 2011 screens than you ever remember it (especially if you’ve kept using them with older versions of macOS in the meantime).
That’s yet another reason (and, to me, the most importan) why I second all those suggestions, and will add that a 27’’ 4K screen, even with a 5K resolution downsampled to 4K to make the UI scale match up with that of your old TB displays, looks much better than any non-Retina display, especially when it comes to text rendering.
I know that, because I’ve been using an LG 27UK670-B display just like that, paired to my current 5K iMac, and although the iMac’s panel is indeed noticeably better (and MUCH better than that from my old OG 2009 27’’ iMac, which was roughly equivalent to your displays, or the older 24’’ Philips screen I was using before, which had the same pixel density/ppi value), the cheaper LG is, in fact, so good that I’ve bought another one to pair them with the Mac Studio I’ve ordered a few days ago.
