Im using an old Samsung LCD TV for gaming but I think the input lag is noticeable especially when playing fighting games. Therefore Im thinking of using a monitor that has a lower input lag instead.

Are all of you using TVs that have low input lag?What's your TV model?

Response time =\= input lag.
Input lag would be significantly higher than response time.

Some BenQ TN panels monitor have 1ms response time.

im aware of the difference.

based on this
https://www.displayninja.com/input-lag-vs-response-time/

shouldn't I prioritize reducing input lag?

1ms input lag is next to impossible for a monitor/tv.
Most companies will not display their input lag, you’ll have to rely on third party test results for those.

I'm using this monitor for both my PC & PS4. So far so good on PS4. can feel the difference palying BF1 using this than my previous 24ms Acer monitor ans Sony TV.

https://www.asus.com/us/Monitors/VG275Q/ProductPrint/

Can consider the Dell 24" Gaming Monitor: S2419HGF
It's a 144Hz with 1ms response time monitor.

Thanks guys. I got an XL2411P instead.
it's alright so far but the factory settings were terrible.

You can try to test for input lags.
However, test shows that it's hard to reduce the input lag to below 100ms on the PS4.