Are both cables suitable high-speed cables? Or in other words, does the direct connection to the PS5 work with both cables or have you only tried it with one of the two cables?

I have now tried it out briefly. My Apple TV is normally connected to the TV with 4K SDR 50 Hz indirectly via my AV receiver, because my receiver can't handle any more. I have now connected the device to the TV without a diversion via the receiver, but through the splitter, and switched to 4K HDR 50 Hz. It worked for me. Unfortunately, I only saw now that you wanted to try 60 Hz. I don't know if the connection would always remain stable for hours, because I only let it run for a minute, but I didn't notice any problems during this time. My experience shows, however, that in the end it is usually the cables that are to blame, or that the source and target devices simply do not "understand" each other properly. At the moment, for example, I even have situations where a connection via 4K works better than via 1080p. Or HDMI cables that work better than others when connected directly, but as soon as a splitter is in between, the supposedly worse ones suddenly work better.