All the Galaxy S20 models in the US are compatible with 5G networks, but the Galaxy S20+ (SM-G986U) and the Galaxy S20 Ultra (SM-G988U) are superior to the Galaxy S20 in terms of 5G connectivity. They support both mmWave and sub-6GHz 5G networks, and are the first truly all-carrier unlocked 5G smartphones in the US.
The Galaxy S20+ and the Galaxy S20 Ultra will work across all major carriers in the US. Even if you don't buy unlocked versions of the phone in the US, there would only be a single hardware version of the phones in the country. Although, they would come with the firmware of the respective carriers. If you buy an unlocked version of either of those phones, you can insert a SIM card from any carrier and enjoy the fastest possible 5G speeds on the network.
Galaxy S20+ and Galaxy S20 Ultra support all forms of 5G networks in the US
If you buy a Galaxy S20+ or the Galaxy S20 Ultra from any of the carriers in the US and decide to unlock it at a later stage, you would be able to use the 5G network of the carrier that you're switching to. The phones support all the 5G bands that are used (or are going to be used) by US carriers. The 5G bands supported by the phones in the US include n2, n5, n41, n66, n71, n260, and n261, and there's support for DSS (Dynamic Spectrum Sharing) as well.
The two phones also support 2G, 3G, and 4G cellular technologies across GSM and CDMA networks. It is also being reported that the Galaxy S20+ and the Galaxy S20 Ultra also support features like CA (carrier aggregation), SA (standalone) 5G networks, VoLTE (Voice over LTE), and VoWi-Fi (Voice over Wi-Fi).
The Galaxy S20+ and the Galaxy S20 Ultra might not work properly on 5G networks if you travel to other countries, though. However, you would still be able to latch onto almost all 4G networks worldwide. If you buy the unlocked version of the Galaxy S20 in the US, it won't be able to connect to Verizon's 5G network since there's no support for mmWave on the phone.
