Will this Mac mini setup work as I intend? I'm thinking of switching to a Mac mini setup, this one in particular:
New Apple Mac mini (3.6GHz quad-core 8th-generation Intel Core i3 processor, 8GB RAM, 256GB) — https://www.amazon.co.uk/gp/product/B08636S4KV
For my display, I'm thinking this 24 inch Dell P2415Q 4K IPS Monitor — https://www.amazon.co.uk/gp/product/B00QAJ2MOM
Would a Mac mini be able to output at Ultra HD 4K 3840 x 2160 resolution so that I can make the most of the display? or would I be better off buying a lower resolution display?
Also I've noticed the Mac mini only has two USB ports, I could do with 4 in total, for the following:

Phone charger
External hard drive (for Time Machine backups)
Keyboard
Mouse

So I was thinking of buying this 4-port USB hub — https://www.amazon.co.uk/gp/product/B00Y25XFGK
But I think I've had problems with these in the past, where they don't generate enough power for certain devices. Am I likely to have this problem using this with a Mac mini?
The 2018 Mac mini can output two displays at 4096 x 2304 from its Thunderbolt connectors, and one 4096 x 2160 display via its HDMI port.
So a single 3840 x 2160 display is well within its capabilities.
The mini has 2 USB A ports, but 4 Thunderbolt ports, which also provide USB C. You could use a USB C to A adaptor or cable to connect a USB device.
I have a mini with an Anker 7-port USB hub, and that powers both my iPhone and external USB drives. My iPad, however, does not charge through the hub. Keyboard and mouse take minimal power. You might want to connect the drive to the mini directly, and the hub to the 2nd USB A port.
Most hubs do come with an optional power supply, but I would expect that would only be needed for multiple high-power devices.