The number of posible combinations exceeds 2.6 undecillion potential pairings.
The number of all possible phrases that contain 12 words, out of 2048, with word repetition, is 2048
12 (~54.4 duodecillion). However, not all phrases are valid, because the last word contains the 4 bits checksum. This reduces the number to 2048
12 / 2
4 (~3.4 duodecillion). None of these numbers begin with '26', so I'm not quite sure how you got this number.
24 is obviously more secure, but harder to keep.
It means 24 words are safer in security than 12 words, 256 bits of entropy compares to 128 bits of entropy. 24 words are more secure than 12 words.
Bitcoin private keys provide a 128 bits of security. A seed phrase can be 128 bits, 256 bits, 4096 bits, it won't provide security beyond 128 bits.
Maybe a 24 word seed phrase will however become more relevant in the future when there is more and more computing power available. Is there any calculation if it will be possible to crack 12 word seed phrases with a super computer maybe in the next 50-100 years if you take into consideration how fast the capacity grows?
Let me put it this way: It's easier to work out the private key given a public key than guess a seed phrase with money inside.