emacs-from-scratch VS doom-emacs

I am building an emacs config, I have got a list and plan of what I want, but I am not sure where I start building, are their any guides or docs on how to build a config from scratch, explainations of concepts like lazy loading, how the different package managers work and what they do, and all the built in emacs concepts and features I have gone though this tutorial, but it doesn't explain anything and doesn't show how to customise anything.

Check out the YouTube channel System Crafters, he has a multipart series "Emacs From Scratch" where he goes over setting up his Emacs installation and setup, and other videos showing how you can do all sorts of things.

There are guides and even video series that cover a lot of beginner stuff. masteringemacs.org has a lot of great articles, and the System Crafters YouTube channel has a lot of great looking stuff.

Hey, I recently set up mu4e following SystemCrafter's guide and was pleased to find everything worked upon setup.

This Youtube Channel has a lot of emacs development, even there's a course to learn emacs lisp.

Depending on what you are looking for, System Crafters has a lot of Emacs content.

A bit older http://emacsrocks.com One of my favourite episodes being http://emacsrocks.com/e13.html the ending is just awesome.

System Crafters yt channel is much newer and also amazing https://youtube.com/c/SystemCrafters

You can take a look at the default init.el file for Doom emacs here, as you can see, there is a :lang section where you can uncomment support for commonly used languages. Although you generally don't change the init.el file too much, usually, it is there to load your actual config files. If your language is not supported out of the box, there are ways to add packages (a.k.a. "plug-ins") in packages.el. And you can add customizations in config.el.