So Ledgers nano seed phrase backup with those companies is now subscription service. Ledger Nano wallets are the worst hardware wallet that someone can go for.
Q1: Doesn't that kind of negate the value of the wallet, if keys are stored OFF the wallet?
It makes the wallet to be worthless to me. But your seed phrase backup should be stored someone offline in two or three different locations.
Q2: Is this $9.99/mo subscription mandatory? It didn't leave me much option?
I know the third party backup is not mandatory. But why would they include such thing.
Q3: Can I use the nano 3, just like it's advertized, without the subscription? I can write down my own keys and manage them myself.
The third party backup is not mandatory.
Q4: Is there anything I lose, that's important, if I don't buy the subscription?
You lose nothing but you gain something because nobody will know your seed phrase but only you if you protect it very well. You can even add passphrase to make it more secure offline.
Q5: Are there any important advantages, if I keep the subscription? $120/year sounds expensive to me.
They are just looking for more money. It has no importance to me.
Q6: I have a coinbase wallet. Is that a hot wallet, or some other kind of wallet.
Coinbase.com is a custodial wallet but they have a wallet which is noncustodial. If the wallet has seed phrase, it is noncustodial. But it is close source and not recommended.
Q7: I also have Electrum wallet. (was just experimenting in 2017, and didn't know I had a seed to remember, and lost my password. Just the other day, I was looking at some notebooks, an found the password. It worked, so I recovered that account. Unfortunately, it only had $29 in it. Cheesy
This is not a question. But it is worth knowing that only the seed phrase is enough to access your wallet. If you forget the password, create a new wallet and import the seed phrase and set a new password.
Q9: Is the nano X better than the S? I know it uses bluetooth?
Nano X is supporting more coins.
Q10: Finally, what is the most secure cold wallet? Are they beter than the hot wallets, like codebase wallet?
Those airgapped and open source ones like Foundation Passport.