PJ87
Journeyman Pro
I refer you to post #9.
The wireless adapter in a device is rated to a maximum speed. The older the device, the higher the probability that it will be a slower adapter.
My brand new laptop for some reason kept locking itself to our meshes network 2.4ghz .. speeds of like 15
So I disabled the settings so it can't see 2.4ghz and it forces it onto 5
Speeds of 70 returned
Like you say.. what the device can receive is key