This is interesting about Estonia, but overall even though it's more difficult. the D7 visa for Portugal would probably be much better and still possible for most in the retirement category.
Estonia, too cold, and I would be worried about Russia.
In my case, I could qualify for Portugal, but would prefer Spain if I moved to Europe, but I don't qualify for that.
More expats are moving to France which can actually be affordable in the provinces, though I'm not up on the requirements.
For people with distant Italian relatives to be mined for residency, Italy is also popular.