I can confirm that I successfully activated a Sprint branded Galaxy s10 plus pre-ordered from the Samsung shop app. It was delivered to me today and I took it to my nearest boost Mobile store and it was done in minutes!! So far it's flawless and I'm super happy with it. Also I opted for the sprint variant instead of the unlocked variant when I pre-ordered because from my experience carrier branded phones receive updates faster then the unlocked phones.
To answer your questions I used the Sim card that was already pre-installed in the phone when I took it out of the box it does say sprint on it though, also if it helps it did include another Sim card kit with the phone with an extra Sim card that I didn't use the Sim part number is SIMOLW416TQ I'm guessing you would need that Sim card kit.