the worst programmers write many lines that do less while great programmers write few lines that do more.

That doesn't sound exactly right. Readability is IMO the most important code quality followed by things like maintainability. Conciseness is a lot further down the list. If I have to use more lines of code or even leave out a little performance optimization for readability, I generally do.

It should be possible to configure DoH in Firefox settings under "General" - "Network Settings" right at the bottom.

Have you considered switching to AdGuard Home? I think it supports DoH in both directions and provides most if not all that Pi-hole does.