A few things
1) the fingerprint sensor in display works with some screen protectors on the Oneplus 6t which is using optics
2) The tech used on the S series is going to be different and is inline with what Qualcomm Just showed off with the snapdragon 855. This can be used with a screen protector even will work if the screen is a little dirty. Google it
3) Samsung and other Manufactures will offer both 5G and 4G device options. The 5G option will be considerably more money.
4) 5G is only going to be available so far in 2019 with Verizon and ATT in limited markets.
5) Its a little bit of a mess on standards for 5G because Verizon is using one technology to deliver 5G and a company like Tmobile will be using another.
6) I hope carriers offer the option for 4G devices for the next few years because I don't want to pay more $$ for something I may not be able to use.
7) In closing, from the Qualcomm event 5g, is going to take several years to have a meaningful deployment outside major cities.
8) Oh Yeah, you'll be paying more too for the service