Can the M80q Tiny run two or three monitors?

Yes. It has one DisplayPort and one HDMI output, and the USB-C port can drive an additional display with a suitable adapter. That covers two or three screens for office work.

Is the memory and storage upgradeable?

Yes. It has two SO-DIMM slots and supports up to 64 GB of DDR4, and the SSD can be swapped for a larger drive. Opening the case takes only a few screws.

Only light or older titles at low settings. The Intel UHD 630 is integrated graphics, so it is built for office apps, browsing and video, not modern games.

Does it come with a monitor or keyboard?

No. It is a desktop-only package, so you need to supply a monitor, keyboard and mouse. It does include Wi-Fi and Bluetooth, so no network cable is required.

How does it compare with a full-size tower?

It uses the same class of Core i5 and DDR4 memory but in a much smaller case with a 65 W supply. You give up expansion slots and a full-size graphics card in exchange for the small footprint.