I get 10mbs at home. When I experimented with TM on my iPhone eSIM I would get 40mbs.
For the last month or three with one bar I would on occasion get 40mbs on Sprint.
I just chalked it up to having such a weak Sprint signal I would roam over to TM.
What I don't know is if being in Chicagoland would TM be set up as a Sprint roaming partner.