Flow:
I have 2 PCs using flow. The main one has 2 4k monitors side by side and my mouse and keyboard is connected via a unifyiing dongle
my second connected to Flow is a laptop with 4k display that sits below middle of the main's 2 4k monitors. I also use a unifying dongle.
Flow seems not to stay consistent. often if moves up and down between PCs smooth but then it will just stop working and i have to switch PCs manually on my mouse and keyboard to recover.