How I’d go above this is dependent on how much storage you expect to be using mid term/until you want/can buy another drive.
Must have 7TB ? Swap the 10tb for 2x4TB, then do 4TB parity 4+2+1TB as Data drives.
Is 3TB enough for the time being? Keep the 10TB and use as parity, 1+2TB as Data drives. When full, go for up to another 10TB as Data.
That second option is more upgradable in the future.
I’m guessing everyone meant Data drives by saying “pool”. In unraid, Data drives are the ones protected by parity, in the array. Pools are “out of the array”, not protected by parity.