You need to register to use the wallet, and I think it's also very useful to use and it's very nice to have it later.
This is a lie, what are you even talking about? Online wallets? Learn the difference.
Electrum had a phishing attack going on, but it wasn't vulnerable, only the users believing the fake message. Same as people receiving bogus emails, you should ignore and discard them. From v3.3.3 onward, Electrum no longer displays messages from servers so this problem is resolved.
Of course you are free to experiment and pick one of many wallets.
The "Light" wallets sync immediately, while others need to download the entire blockchain (which is approaching 200g). Although you are not required to keep the whole blockchain locally, you can help the Bitcoin network by keeping it, especially if your internet speeds are above 10mbps.