Wi-Fi Mesh, Repeater, Bridge or Extender

Looking for some help with Wi-Fi issue please.

Main issue is my wife's T-Mobile Pixel 3 that freezes or buffers on my Spectrum 300GB internet. T-Mobile says the issue is Sprectrum Wi-Fi and I do have a Roku TV that buffers too much to my liking and my ethernet desktop buffered once for the first time ever watching Paramount+.
My 3-story house is only 2000 Sq Ft and I never have more than 6 devices on a 5G dual band Wi-Fi at the same time. I have had the router in the basement for years without issues (but less devices), so I moved it the middle floor and the Roku TV says it has an excellent connection that still buffers.
I don't think I need an expensive mesh system, but I was considering a new 6G router and maybe bridge it with the old 5G router. Alternatively, I could switch to Google Fiber or Xfinity but that is no guaranty either, but Spectrum is way too costly for the occasional DVR pixelation and freezing that comes with it.

I just thought the old days of buffering were gone but I guess there is no escape, thanks for your consideration.

Devices has zero to do with this, it is where you are using the device, what is if any using all of the available bandwidth of the connection, distance from nearest Wifi AP. If you only have one single Wifi Access Point and signal is not best throughout the property, then put in a Mesh system with multiple Access Points to give enough coverage.

Thank you for the great ideas, I will certainly give them a run. I imagine this will take some time to sort out.
Going to try the easy/cheaper ones first and work up from there, in my first attempt I have configured the Pixel to have one Wi-Fi band all to itself.

bro67 said:

"Easy & Cheap" do not work and cost more. Spend the money on a decent mesh like the Linksys Velop with at least a minimum of 3 units.

Don't forget Netgear.

Hi John, thanks for keeping me honest, I don't remember all the electronic nomenclature like I used to, it's 350 Mbps down & 9 Mbps up split into Cat5e, 2.4 GHz & 5 Ghz bands. Seems to me that should be more than enough with the few devices I have. Sprectrum is overpriced but it's only second to Google Fiber in my area.

Just me personally, I never will be a fan of Wi-Fi, don't even use a cell phone. If it was anything other than my wife's phone I wouldn't bother.

As usual I am my own worst enemy I reset the router to its default settings and all is well.