I have understood a little more out there but only bip39 uses a Mnemonic seed? Because many wallets from different manufacturers are often compatible.
Assuming I have a 24 digit Mnemonic, example of the website you linked:
the seed is out:
Is this the entropy at the same time?

if i now add a 128 digit password:

the seed becomes:

In the hey area the f at the beginning is higher than the 1 so seen like this almost 8 times as strong, or how does this entropy calculate?

Background of my question is simply that I want to create a wallet that is as secure as possible but where also the address looks cool as generated by vanitygen.
If I wanted to create a wallet here now, how could I influence the entropy?
https://github.com/adrijano/Bitcoin-wallet-cracker

Ich könnte mir ja auch mit den Links die du gesendet hast offline eine walleterstellen aber ich kann den Quellcode nicht sehen und es könnte ja anbieter geben die millionen von wallets erstellen und speichern und nur diese erzeugt werden und mit dem anbieter verbunden sind, auch wenn man es offline generiert, wenn es aus vorgenerierten Seeds ist, bringt das ja alles nichts.

I could also use the links you sent to create a wallet offline but I can't see the source code and there could be providers who create and store millions of wallets and only these are generated and connected to the provider, even if you generate it offline, if it's from pre-generated seeds, it's all useless.