If you have time, go to
Coinmarketcap, choose the first 20, 50, 100 (as you like) coins/assets, go to google, type Xcoin ANN (where X is the coin's ticker and ANN being short for announcement), this should bring you to coins' official announcement threads on this forum, and read as you like. This is tedious, but there is no better way to find that which you seek in order to be convinced. And don't take anyone's blabber for real.
Thanks for the tip. It is tedious, but I may resort to this. But I am hoping to avoid doing the work all myself? Surely many thousands of people have asked "What are the differences between all these cryptocurrencies"?
There must be a website with a quick blurb on each, or a chart comparing them?
One thing that stands out is how many are wholly original, and how many merely build on original Bitcoin code? I have no idea if 90% are copies of bitcoin, or 10%, or somewhere in between? (Ones that are based on Bitcoin code I will dismiss outright; I want new code. Or that this pint *think* I want new code.)