external monitor size

I have a 21.5 inch iMac late 2013 (2.9 GHz i5)

Wanted to know if I had two external monitors what would the max resolution I could have on them be?

So if I bought two Dell U2518D which has a max resolution of 2560 x 1440 at 60 Hz would I be making use of the max resolution on both displays.

Also if I cant get the full resolution of 2560 x 1440 at 60 Hz, what would be the difference in me buying two
Dell U2417H monitors? would the text just be slightly smaller than on the Dell U2518D?

Thanks in advance

This, https://everymac.com/systems/apple/imac/specs/imac-core-i5-2.9-21-inch-aluminum-late-2013-specs.html, shows you can use 2 monitors with Thunderbolt connections at 2560x1600.