4k is not supported on many older models. Check your official specs. Most Macs has max 1440p@60hz output. 4k is only supported @ 30hz, which is no good for daily usage. And the main problem is, if you get a 4k monitor( to future proof your setup), and try to use it at 1440p, everything will be blurry and pixels will shift and distort.
Just get a native 1440p monitor.
If you have a never Mac, getting a 4k 27" monitor may still be a bad idea. Since 4k is too much for a 27" screen, you will need to use scaling in Mac options, and ideally set it to "looks like 1440p" But this will cause your mac to do 1.5 scaling and create a burden in your GPU and CPU. It will render everything doubled at 5k and try to scale it to 4k. If you're using a Macbook, your fans will never stop even on idle. This is even worse performance than getting a 5k monitor and using it native 2x scaled, which is easy on GPU.
One side note; there is no USB-C Hub that offer 4k@60hz output, technically not possible. You have to get a separate hdmi or dp adapter, or an expensive Thunderbolt 3 dock. But there are some usb-c to hdmi or dp adapters which also offers Power Delivery.
I've already wasted money and time figuring this out, so you don't have to :)