nerdwallet.com
I don't work for them and I don't benefit in any way from mentioning them.
I found their explanations and charts to be really clear and helpful. I did not buy through them.

Under age 65
Medicare eligibility for people under 65 depends on the laws of the STATE that you live in.

Impartial medicare advisors
The federal government has mandated that every state provide the public with trained medicare counselors for FREE. So check your STATE level information, too.

Medicare RATES
Can vary by the COUNTY that you live in. So, if you're planning a move, don't forget to consider that.

For people who already have gone through the process of choosing medicare:
We really should try to educate our family and friends about the process/ warn them how long it takes. Three months of hard work was not enough time for me to find information and to understand it and to make a decision that I felt good about.

It's almost like there are TOO many options now.
And you have to be careful not to get ripped off, or to succumb to advertising and "counselors" who do NOT have your best interest first.
And federal- and state-level considerations. [My state Pennsylvania has a lot of protections for seniors and disabled under 65. Some states don't.]

I had to do a lot of reading. The information on the federal government's website is useful. My state has a good website, too.

All these websites are useful but reading on the computer really tires out my eyes and so the rest of my body, too. You may want to budget in time for fatigue, too.

That's my 2 cents. Hope it helps somebody. Have a good day!