So when using a 4K TV for PC gaming, do we still use the TV's Game Mode option ?

I use my 4K TV for console gaming and PC gaming. So I use the TV's Gaming Mode for whenever I console game. But seeing how I'm using the PC input for source for PC gaming do I still enable Game Mode also ? I'm asking cause the source input is set to PC and by doing that it already grays out some options in the picture settings so I'm thinking it's the kinda like a Game mode for PC's.

Gaming mode is to reduce latency (lag) but at the cost of quality or options that need the onboard processor.
My Samsung Q9 has such low latency I dont use gaming mode which lets me use the HDR+ setting.

My Samsung TV (Q7F) can do Game Mode on PC, but I found switching to Game Console input resulted in better colors and a better experience (especially in combination with HDR).

Depends on the model. My Samsung KS7005 (Nordic KS8000) has better image quality in the "PC" mode but it also comes with higher input lag. Newer models are apparently better in input lag between modes.

For Sony, yes using Gaming.

Samsung NU8000

https://www.rtings.com/tv/reviews/samsung/nu8000

It's a good 4K TV.

In the settings it says to use Game mode it's not specific for PC.

This is the quote:

"GAMING SETTINGS
To enable Game Mode, select 'External Device Manager' from the 'General' menu, and then select 'Game Mode Settings'. Set 'Game Mode' to 'On'. For SDR gaming set 'Sharpness' to '0' to remove any sharpening. To enable chroma subsampling when playing from a PC, set the input icon to 'PC' under the 'Input Device Manager' submenu."

I've set the input to PC but not game mode. For all I know it's meant for consoles only.

I just want to know if I'm using PC mode do I still use the game mode too ? I'm maybe thinking PC mode is good for text and chroma subsampling but I'm still getting the most input lag. That's why I still need to use game mode.

Yes, use Game Mode if you want the least lag.

On My LG C7, the input lag is identical between labeling the inputs PC and Game, but the colors are much better when I use the Game mode (especially HDR).