Hi, apparently you can split the screen into 2, and there are 2 HDMI input sockets at the back... but I've never tried to connect 2 PCs.
(I'll be back from holiday in a few days... I can try if you want to wait...)
Frame in frame is used in photography, but you want to use 2 PCs with 1 single screen, is that OK?
Best regards Pierre Gervaix

Yes, but with this monitor it is called Picture in Picture.