This monitor is actually only suitable for PCs.
Sure, you can connect the Xbox, just like any other console, but the 165Hz display can't be used properly because the consoles can only manage a maximum of 60fps (usually only 30). So it's a waste of money.
This can be an indication that the cable or port used on the graphics card has a problem.
I have the same monitor, but in my case it was one of 4 ports on the graphics card that didn't want to.
It may also be a defect, but it makes sense to check the possible causes mentioned above first.
What kind of graphics card did you connect the monitor to?
I don't have the flickering, but I also have the shifting of the 1mm and it's starting to confuse me. ASUS seems to have a firmware update, but this can only be done by sending in the monitor. A workaround for the 1mm: Either switch the monitor off and on again, or overclock the monitor to 165hz. This is possible in the monitor settings.
I would have difficulties there too :)
So: Both are equipped with a TN panel, you are sure you don't want an IPS panel? TN panels are good! But they have a worse viewing angle than IPS panels and display blacks worse. But they are more solid and cheaper and have a better response time -> good for shooters!
The Asus has 165hz, the Dell only 144hz -> but 144 hz should be completely sufficient. You probably won't be able to experience 165hz with a 2k resolution.
Dell has made many good monitors, so you won't be making a mistake if you buy the Dell.
Go for the one you like better in terms of looks, both are good!
Yes, that is normal. Now you have a fast monitor for gaming, but before you had a monitor with a better panel. The Philips 298P4QJEB had an AH-IPS panel and the ASUS ROG Swift PG278QR only had a TN panel.