I use 43" 4k LG UH603V. Panel is 100Hz ( iirc ). My previous monitor was 40" FHD Samsung TV 60Hz. And monitor before that was 19" Philips 4:3
I think it goes down to following - if you play competitive online games some supper low ms gaming monitor will be of course better choice.
I sim only so I don’t care if the panel response is 4ms, 8ms or 20ms. But I will never go smaller.
One thing to consider is also pixel density. For example if you are used to standard 24" HD monitor then 48" 4k monitor/TV has the same pixel density.
In normal words, pixels on my 43" 4k TV are smaller than pixels on 48" 4k TV and so on. It means that I don’t need so excessive antialiasing as would be needed on 48" / 50" / 55" TVs/monitors. You will definitely see the pixels in game on 4k panel if it is that big.
You can maybe check Philips. They offer big format 4k monitors with low ms, 4-5ms, for reasonable prices. Eg. 43" Philips BDM4350UC or 43" Philips 436M6VBPAB ( in EU; the designation may be little different in each country ).
Definitely standard 4k TVs goes for lower prices as dedicated monitors. And apart from mentioned TV picture modes I would also avoid any highly sophisticated TVs with lot of functions. Less modes, less functions = less picture processing = more fluid picture imo.
Also, I am sitting cca 80cm = 2.6ft from my LG. No problem with eyestrain. To contradict a little my previous statement about modes and functions, one particular mode is very useful. It is called EYE COMFORT MODE which turns all colours to warm tones. Very comfortable indeed