all drives in a RAID should be identical drives. putting dissimilar drives together in a RAID will work but is never suggested.
the slowest and/or smallest drives will hold everything back, hindering the RAID's performance and/or logical drive size.
combining a 1TB and a 3TB into a RAID 0 or 1 will essentially waste 2TB of the 3TB . combining a SSD and HDD into a RAID of any kind will essentially waste the SSD's speeds.