Is the HP Pro 400 G9 Mini good for everyday office work?

Yes. The Core i5, 16 GB of RAM and SSD handle email, browsing, spreadsheets and video calls without strain. It is not built for gaming or heavy creative work.

Can I upgrade the RAM or storage?

The memory ceiling is 16 GB, so it ships maxed out on RAM. The 512 GB SSD can be swapped for a larger drive, but the compact case limits expansion.

Does it have Bluetooth?

No. Bluetooth is not included, so you will need a USB adapter for wireless peripherals or headphones.

Does it come with a monitor or keyboard?

No. It is a desktop-only package, so you supply your own monitor, keyboard and mouse.

How does it compare with the Lenovo ThinkCentre Tiny and Dell OptiPlex Micro?

All three are compact business desktops with similar Intel chips. The HP matches them on ports and adds Wi-Fi 6E, but its 16 GB memory cap is tighter than some rivals that accept more.

Is it good for a home office?

Yes, if your work is light to moderate. Its small footprint and quiet fan suit a home desk, but check you don't need Bluetooth or more than 16 GB of RAM.