The issues described by you guys are exactly the issues that I encounter. I have contacted support which suggested that I should deactivate all Power Saving options but the situation didn't improved.
I always had to re-plug and/or Power-Off and On the monitor after waking from sleep(both on MacBook and Windows laptop). I had the drivers for windows installed, so it should be working as expected when I paid 1400€ for it.
Then I bought a high quality USB-C cable which support DisplayPort 1.4 to replace the original Samsung cable and the situation improved a little. Now re-plug was not needed anymore, but the KVM/USB Hub still was still not able to do the job properly, and that 5-10 seconds delay after connecting the monitor or wake up from sleep is super annoying. Also, if I let my MacBook sleep overnight while connected to the HUB, I will find it crashed and rebooted next morning, every single time.
I have contacted the Support and had a lot of particular discussion with a guy there who tried to explain that the behaviour is normal whatever I would complain of... In the end he suddenly didn't answered me at all. Great support Samsung... your Switzerland Support team is useless.
Then I decided to give up with the useless hub so I bought a USB-C <-> DisplayPort1.4 cable with Power Delivery injection from Amazon so now I have both Display and Charging over a single cable. Fortunately the keyboard and mouse is over bluetooth so I don't use the USB hub anymore(a feature that I paid for extra). The good news is that if(and only if) you use the DisplayPort connector of the monitor, you will be able to have native resolution at 120Hz, also on MacBooks 
It worth mentioning that I am a professional IT Engineer with deep knowledge on the Electronics(university + experience) and I fully understand that Samsung did a total mess when they installed the USB-C Hub on this monitor. The hardware on it is super super super low quality, that's why it's so unstable. This is a purely marketing move, on a monitor sold to professionals.
I have a friend, also an IT Professional and he had exactly the same problems with the same monitor. He bought a WD_Black D50 docking station to replace the useless Samsung USB Hub.
Samsung, this monitor is not for grandma which only connects a mouse to the monitor hub, this is meant to be sold to professionals... your USB hub is useless.
Hi Manuel
In short, your plan will work, and you will have 120Hz with native resolution
It's exactly this one that i am using. + a very short 0.3 meter 60W capable USB-C cable which comes from the USB-C of the monitor + a 90 degree USB-C adapter since my HDMI2 port is busy.
This is the 90 degree adapter: https://www.amazon.de/dp/B0BC3CLNHH?ref=ppx_yo2ov_dt_b_product_details&th=1
USB-C from Monitor can provide charging so it will work, but the other one(PC-IN) will not charge your laptop.
The "problem" however, is that you have to deactivate System -> Auto Source Switch since when you wake up your laptop, will sometimes detect a device connected to USB-C IN(from where you get the power), and will switch the source to USB-C instead of DisplayPort.
Best regards
Casian
