While a 2-of-3 split is a good enough backup strategy, the K-of-M generalization is sometimes needed for sophisticated use cases such as social recovery.
It is worth noting that the K-of-M split uses a different algorithm, known as Shamir Secret Sharing Scheme. Compared to the 2-of-3 split, this method takes exponentially longer to perform as K (the number of shares needed for recovery) and M (the total number of shares) grows. However, the recovery time increases linearly.
Tweaking a share consist of replacing its characters by the corresponding tweaked characters:
Recovery can be achieved by deriving the secret (seed phrase + checksum) from the gathered shares. The tweaking factors have to be determined using both K-of-M wheels as explained later.