For international travel and at home, the following may help.
My wife's Note 9 is a Verizon variant and we have Verizon as our provider. We've visited the UK several times this year and upon arrival purchased "pay as you go" SIM cards from 3. No issues at all and had solid 4G/LTE coverage in areas where it was available. Phone calls and SMS worked to other landlines/mobiles in the UK, although we primarily used Hangouts for messaging. We purchased plans with 12G data, and ahead of time downloaded Google Offline Maps for the regions we were visiting, so zero worries about running out of data.
May not be quite as affordable as the T-Mobile international option or regular plan costs, but on the positive side we have solid (albeit not the most affordable) service at home (large US city, and my wife primarily works at home, so WiFi is always there minus when Spectrum decides to have unplanned outages). For years we have discussed going with T-Mobile, or more recently maybe Google Fi; but since on average we may go outside of the US once a year (this year was an exception) reliable and broad coverage at home and around the US eventually wins out.
Now that Google Fi supports a broader range of phones, that is on our "list", and if either of us were to travel internationally more frequently, then Google Fi would likely be our choice.