Would you advise me to create the three seeds through the electrum software or through
https://iancoleman.io/bip39/ (BIP39) ?
What would you be the pros and cons of each method?
Still Electrum seed if you're going to use Electrum.
The cons of using BIP39 seed is you'll have to take note of the script type and the extra steps when restoring them.
And also, there's a possible future compatibility issue since it's not advised by Electrum itself. (
check the "Warning" when restoring BIP39 seed)
The pro is of course, it's compatible with almost all non-custodial wallets.
With Electrum seed, you can directly restore them in Electrum without taking note of the script type.
Anyhow, both backup should still have a note of your selection of "
m-of-n", number of required signatures and number of cosigners.