Best Altcoin as a Base for Learning

I'm interested to learn altcoin creation. I've been doing C++ for some time but in a much different area.

I want to find out which coin would be best to work from as a base and start to digest and understand. I have read considerably on the forum, but this is a matter of particular insight, and changes with time.

I am NOT interested in making another shitcoin, I'm interested to learn. I have a developed career and I'm a published author on a technical subject with one of the "big three" book publishers.

Someone suggested using the latest Litecoin version, although a portion is removed from it for creating a genesis block, and that it does not protect against the 51% concerns. Also, I've been told there are other bugs and issues still in the current Litecoin version but avoided with other coins.

In your view, what's the best open source coin that includes all the latest Litecoin fixes, avoids the known bugs remaining in the latest Litecoin version, avoids the 51% problem, and still includes the genesis block creation code? Alternatively, should I just stick with the Litecoin code and add the genesis block creation code back in as I learn?

Thanks and appreciation to all who respond in kind, as the community (understandably) seems protective about newbies.