@Shonky 

I have set of Deco M9 Plus units and Gigabit Internet.

Everything that is connected by Ethernet cable through Deco M9 wired to home network will get gigabit speeds, because M9 has gigabit Ethernet ports.

Wireless connection to M9 will be limited by WiFi5 and will not reach gigabit speeds. If you want, at least in theory, get gigabit speeds on wireless connection, you'll need to look for WiFi mesh that supports WiFi6. Also wireless device that will be connecting to it must support WiFi6.

I like my Deco mesh and plan to keep it. Also, I haven't found much difference in how my home network behaves at 1 Gigabit ISP Internet comparing with 300Mbps I had previously. Large file downloads from Internet are obviously faster, but I do not routinely download large files from the Internet. 4K streaming needs less than 40Mbps per device, even with multiple devices streaming in 4K simultaneously in average household, Gigabit Internet is overkill.

When my ISP increases Internet prices next time, I will consider downgrading to 500Mbps.

@Alexandre. Hi I have 200mb a present however I had heard through the grapevine there may be a free upgrade to gigabit. My post was to ensure the M9 was "future proof" for this. I'm also not interested in WiFi6 standard as pricing it too high I I don't have any compatible device. Thanks for confirming the M9 is suitable for my situation

@Shonky 

Deco M9 Plus is top of the line WiFi5 mesh from TP-Link. It would be an excellent choice for most people who want simple in setup and configuration yet powerful in performance WiFi mesh.

I am very pleased with it, just make sure you do not trust marketing materials saying you need just two units to cover an area of up to 3,800 square feet. This is not just TP-Link, every WiFi mesh brand gives overly optimistic WiFi coverage estimates.

For a good coverage, the rule of thumb will be to start with one Deco unit per house floor. If you have finished basement and want WiFi coverage there - one unit for a basement, too. 

That would be my recommended minimum. If you have bungalow, or very large multi-floor house, or need to place Deco M9 at far corner of the house instead of close to the middle of the floor, you might need to buy more than one per floor. The thing I like very much about Deco is you can easily add more units to its mesh system. So, if you find places at your house with weak coverage after deploying initial set of Deco units, like I did, you can buy and add more.

For mobile devices that run on WiFi 5GHz expect speeds of up to 500-600Mpbs from Deco M9 wired to the Ethernet (such as Main Deco) and 250-450Mbps from Satellite Decos connected to Main Deco wirelessly. Tested that with gigabit Internet in my house.