Is this TV worth it over a 4K LG?

Only if you sit close to a very large screen and want the 8K panel and 100 Hz motion. For most rooms a good 4K set costs less and looks nearly the same with upscaled content.

Does it have HDMI 2.1 for 8K and 120 Hz?

The listing gives four HDMI ports and a 100 Hz panel but does not state HDMI version. Confirm HDMI 2.1 support with the seller before buying for next-gen consoles.

Can I mount it on the wall?

Yes. It uses a 400 x 400 VESA pattern and the Gallery Design is intended for wall mounting. Check that your bracket and wall can carry a set this size.

Does it work with Alexa and Google Assistant?

Google Assistant is built in, and the TV is listed as Amazon Alexa compatible. You can also control it with the LG remote and webOS apps.

The listing describes the TV with stand and carton dimensions but does not itemize accessories. Expect the TV, stand parts and remote; confirm cables and wall bracket are not included.