I need some advice with my series x 4k TV Details

Yes, The Xbox Series X will play at 1080p fine, but the Xbox Series X is a 4K gaming console,

If you're not planning to upgrade to a 4K TV / Monitor, I'd say it not worth getting the Series X in my opinion, you're much better off with the Xbox Series S as that is a 1080p / 1440p gaming console and you'll save some money if you're staying at 1080p,

at 4:45 has some info on the Series S.

https://youtu.be/7S3s7NCVzDQ?t=285

https://youtu.be/VIHny-XP8jM

You don't need HMDI 2.1 for 4k on the Series X...you only need HDMI 2.1 to run at 4k 120Hz. The Xbox One X only ran on HDMI 2.0 but it output 4k perfectly fine.

This.

My 4K TV is only HDMI 2.0 but it plays games & movies in 4K & HDR10 perfectly fine.I just can't do 120FPS but i;m more than happy with 60FPS

So I can have a tv with a hdmi 2.0 and still play on it

Yes, but if your TV is 4K and you want to make full use of the Xbox Series X 120hz refresh rate at 4K, you'll need a 4K TV with HDMI 2.1,

But again it depends on what TV you have, is it 4K or 1080p? and what HDMI ports does it have ("HDMI 1.4, HDMI 2.0").

I have a lg 4k tv with hdmi 2.0

That will work fine with Xbox Series X,

However you wont get the 120hz refresh rates at 4K, as that requires to have HDMI 2.1, other than that your TV is fine to use, if your not to bothered about 120hz refresh rates at 4K as an issue for you, there's no need for a new TV.

The TCL website has some instructions on how to configure your TV to let the Xbox One X fully utilize 4K: https://support.tclusa.com/20272-roku/268433-will-my-xbox-one-x-play-in-4k-60hz

Verify that your TV is capable of HDR by going to the Xbox One X display settings and open "4K TV details".

In the Xbox One X display settings, ensure you have "color depth" set to at least "30 bits per pixel (10-bit)" to enable HDR.