1. Ledger claim that they have no access to the seedphrase, unless you decide to share it with them. I haven't been following the latest news though, so I could be wrong.
2. It shouldn't be necessary, no. and I definitely wouldn't recommend doing it.
3. As I have said above, it shouldn't be necessary, so nothing important. Just make sure you store your seedphrase safely offline.
4. Definitely not. You're not missing on anything.
5. The private keys are derived from the seedphrase. Each one of your receiving addresses is linked to a private key. The private key is what let you spend the funds from that specific address. If you have the seed, you shouldn't worry about all of that.
6. A coinbase wallet is a hot wallet yes.
7. Electrum is also considered as a hot wallet, unless used otherwise (but the main difference compared to coinbase here is that its open source).
8. You should be able to use it. The ledger live app is available for both android and PC.
9.  It's mainly the bluetooth. Here's is a detailed comparison between the two devices: https://shop.ledger.com/pages/hardware-wallets-comparison
10. Go to the hardware wallet board, there are plenty of similar topics: https://bitcointalk.org/index.php?board=261.0