using embark, you need to set a keybind to embark, then use the ripgrep normally, when the minibuffer returns the results, call the embark via keybind and use embark-export, that is bind to E, then embark will create a buffer with the results from minibuffer

there is some ways to solve this, one is not creating this kind of files, not recommended, another way is changing the path are this is saved, setting `backup-directory-alist` and `auto-save-file-name-transforms` you can change where this files is stored, you can also use no-litterring to this.

to use asap emacs to programming, you will only need a lsp frontend, for example, eglot is now a built-in package, or lsp-mode, another lsp for emacs, if you configurate this package, you have a minimal ide on emacs.

Then when you have time, you can search about a completion frontend, like company or corfu, then a theme for emacs, like modus-themes or doom-theme, then you can use a minibuffer ui, like vertico, ivy or helm and to use git, the package is magit.

When you are familiar to emacs, you can see thing like, completion-at-point-functions, `completion-styles and begin to customizing emacs to your liking.

as you said, display-line-numbers do the shift when the cursor change the quantity of numbers in the line, from 9 to 10, for example, maybe if you use `absolute` can help, or you use can try change a fixed width from the line number, so it cannot change the window size.

Also, you can see this example from modus-theme to help you.

using the Modus-Theme, you can disable this features and customize all visual aspects of emacs