Yes, correct.
I've done a lot of digging, and the only concern I've found is that the company is somehow connected to PureVPN.
I'm not paranoid, so for me this is fine. Take your own threat model into consideration.
Funnily enough, Ivacy knows basically nothing about me, since I bought the offer through a 3rd party site. I have nothing registered on my Ivacy account, aside from my email and password.
Yes, you are correct.
If you're using your aliasing-service to "blend in the crowd", just like how TOR works, you may not want to use a custom domain.
For me, the purpose of AnonAddy is first, and foremost, to help me combat spam. Any privacy improving aspects I see as purely bonuses.
I will use the shared domains from time to time though, if I consider the risks to be too high. This goes from posting an email in a public forum, to signing up for a particularly suspicious newsletter for one-time benefits.
As always, you should take your own threat model in mind.