Why does my new laptop look less clear on a 4K TV compared to my old one?

I recently upgraded my laptop, but I've noticed something strange when I connect it to my 4K TV. My old laptop has a 4K native display, while the new one only has a Full HD screen. When I set them up side-by-side on the same TV, the old laptop looks a lot clearer for everyday use like browsing and reading text. This difference isn't obvious during gaming or when watching videos, but it really shows up in regular use.

Here are the specs:
- Old laptop: HP (2016), i7-6700HQ with GTX 960M, native 4K display
- New laptop: ASUS (2024), i7-13620H with RTX 4070, native 1080p display
- TV: TCL C745 (4K 144Hz), using a certified HDMI 2.1 cable
- New laptop is set to "second screen only" mode, not mirroring the display
- It's using the RTX 4070 for the external display as intended.

I've tried changing the resolution settings to 4K at 60Hz and 144Hz, and while everything seems to function, I find that the text and UI elements look overly sharpened instead of clear. I've played around with the TV settings, like sharpness and noise reduction, but I haven't made much progress.

Could this difference be because the new laptop doesn't have a 4K screen? Or am I missing something else, like specific settings related to chroma subsampling or scaling? I'd love to hear your thoughts!