Is the HP EliteOne 840 G9 good for gaming?

No. The integrated Intel UHD Graphics 770 is meant for office and media use, not modern games. Casual or older titles at low settings may run, but a dedicated GPU desktop is the better choice.

Can I upgrade the RAM and storage?

Yes. It uses DDR5 memory and an SSD, and business all-in-ones in this line typically allow both to be replaced or expanded. Check the service manual for the exact slot and drive limits before buying.

Does it come with a keyboard and mouse?

HP business all-in-ones are usually sold with a wired or wireless keyboard and mouse, but bundles vary by listing. Confirm what the specific listing includes before ordering.

Is the screen touch-enabled?

No. The 23.8-inch display is a standard non-touch panel, so it suits desk work with a keyboard and mouse rather than touch or pen input.

What ports does it have?

It offers USB-A and USB-C, HDMI and one RJ45 LAN port, plus Wi-Fi. There is no optical drive or memory card reader.

Is it worth it against a tower plus monitor?

It saves desk space and cabling and includes Windows 11 Pro, but you cannot swap the display later and the 256 GB SSD is small. A tower plus monitor gives more upgrade room for the same kind of office work.