PC in one room, peripherals 5ft away?

Here is the situation I’m facing. My main workstation is located on the first floor, but there are times when I need to be in another room on the same level—about fifteen feet away. I have a spare keyboard, mouse, and monitor sitting right there, and my goal is to set them up upstairs so I can control my primary PC from that distance, ideally without dealing with any frustrating lag.
Is there a reliable way to pull this off without having to shell out money for an entirely new computer system?
As far as hardware goes, I have some network switches and powerline adapters lying around, and there is also a somewhat mediocre computer upstairs that I assume could handle receiving a video stream. 🤔

EDIT: Honestly, I wouldn't even mind running some cables across the floor if I had to, though we're talking about a fifteen-meter trek here.

If macOS is acting up, I guess the best move would be to hook up a weaker machine and just use remote desktop to access the other computer