Metamask multiple wallet help

DMs disabled so scammers can fuck off. Anyway the wallet is empty except for moons.

So, I imported my reddit vault into Metamask and set up Arbitrum Nova and added moons, that's all fine. I have added the metamask extension before and kept the seed phrase but I never actually used it for anything, so when I wanted to add the Vault, I did a new install because that was the way to be able to add my Vault seed phrase. So my previous Metamask account is irrelevant really, I just mention it because I do understand that when you create an account from scratch, it gives you a new seed.

The thing is, I also wanted to use Metamask to connect to uniswap etc, so obviously I would add other funds, but I don't really understand, because I don't have a seed phrase for Metamask itself, only for the imported Reddit vault.

I tried creating a second account but that didn't give me a seed, just a different wallet address. Wouldn't I need to have a separate seed for a separate wallet on Metamask?

I was trying to keep everything separate for safety, but this way it seems like everything is going to be linked under the one seed, but I don't really understand why that is, especially when they would be on different networks.