Is there a possibility to transfer the video & sound from PC A to PC B and the Mouse & Keyboard from PC B to PC A?
I'm out of this age but for better understanding I'm going to provide the following sentence: Playing computer Games in school.
What I imagine is a direct transfer, without any extras or featured lags.
On Linux, there are a number of solutions for remote display and sound. The XWindows system is designed that way from the ground up, and most of the sound daemons (pulse audio, esd, arts) can be set to use a remote machine as the target. And if you're on the same LAN, it can work fairly well. But there are so many options, you're best off narrowing your target.
On other platforms or with mixed platforms, you can look at tools like VNC (but I'm not positive if any of the VNC implementations do sound). If your source and target are nearby one another, you're better off getting a KVM with audio capabilities so you can just share a monitor and input/output devices rather than using the network. You're limited in that case by the maximum KVM cable length; in the case of USB, you're talking a few meters, with PS/2 keyboard and mouse, you can do maybe 100 feet. You can find 2-device KVMs for down around $25, up to several hundred dollars for devices which can use wiring like network cables to get hundres of feet away; but in all cases you're hard-wired locally.
There are many tools to remotely control computers, but none of those tools can do it without introducing added latency. Almost no tools, particularly on Mac can transmit intensive graphics like you would see in a game.
About the best you get these days in remote control is from high-end Windows-based VDI solutions using proprietary protocols that do part of graphics rendering on the client side.
