tmobile wifi gateway vs connecting with google nest mesh

I just signed up for the Home Internet and I was having the same problem of a decent signal on the first floor.  Having to put the router up high isn't the best………… I setup my Google Mesh system with 3 pods.  At first I was getting decent speeds of 30 mbs at the furthest point, but tonight it's less than 1 mbs when connected to the mesh, and I'm hardwired to the pod, but connected to the router via wifi it's around 9 mbs.  My computer connection is about 20 mbs but last night it was 40…………… I so want to dump Comcast, but I refuse to put up with buffering every few seconds…………..  the 2 week trial will be interesting……..