it would give 20 unrelated, randomly capitalized words with random special characters. Would it be good enough?
Maybe, but why bother remembering all that when you could just use the
Diceware method and remember 6 words?
Password managers make me suspicious for some reason. What if you're stranded without one and need to login from some random cafe? You can google War and Peace everywhere.
Any password manager that's worth a shit will have built in ways to easily access it.
What if FBI gets your password manager?
You're probably fucked. Locking your door doesn't stop the FBI, it stops crackheads looking for an easy score.
Can't they just brute force the master password
Any password can be bruteforced, it's just a matter of time. 28 bits of entropy takes a few days. 44 takes a few centuries. A 6 word diceware password has 77.5 bits, and you can have as many words as you want.
See point 3. The FBI is the least of your concerns.
What if your password manager gets corrupted by, say, a hard drive malfunction?
What if your password notebook becomes unreadable because it gets wet or the ink fades? You use your spare copy. Same thing with a password manager.
Now, what if the notebook or the password data gets stolen and someone thumbs through it? The file's encrypted, so all they'd see is random garbage. How about your notebook?
What's the advantage of using one instead of writing your passwords down (excluding the "FBI arrests you and your password notebook" whataboutism Null loves to answer that question with)?
It's easier to make and organize your accounts, you need to remember less shit, and you can use extremely long passwords without having to read and write a bunch of extremely long passwords.
I recommend
KeepassXC, it'll take less time to set up and try the thing than it did to read this.