1. There is large variation in TN displays. I'm very happy with the Acer TN panels I have at home. I find good TN gives me less eye strain than a lot of the IPS panels. IPS is the way to go for photo editing and similar tasks which require color calibration, but for coding, I actually prefer a good TN panel. Again, the trick is to find the right one. Try them at a store, for example.
2. Consider getting one 4k, and keeping the 1080p monitors. I have a 5 display setup like that. It works pretty well, actually. The 4k is great as a main display, and all the auxiliary stuff lives on the 1080p panels.
1. There is large variation in TN displays. I'm very happy with the Acer TN panels I have at home. I find good TN gives me less eye strain than a lot of the IPS panels. IPS is the way to go for photo editing and similar tasks which require color calibration, but for coding, I actually prefer a good TN panel. Again, the trick is to find the right one. Try them at a store, for example.
2. Consider getting one 4k, and keeping the 1080p monitors. I have a 5 display setup like that. It works pretty well, actually. The 4k is great as a main display, and all the auxiliary stuff lives on the 1080p panels.