Nightmare RAID installation

No friend, you dont need to make the change. And doesnt matter the number of drives, you can allways make whatever RAID config you want to. You may even have different RAIDs with the same machine.

As a matter of fact, RAID 0 is the only option for you, as would be unwise to RAID the SSD with the HDD. The ideal set for you is SSD + HDD RAID 0

Nevertheless, RAID 5 nowadays is useless, as external backup storage has become insanelly cheap. RAID 0 is the method everyone is using, no matter how many drives you have.

for raid 5 you need minimum of three hard drive for raid, ideally of same size and type. I would highly recommand you to not use the SDD in Raid as it will ruin both the drive and raid capacity.