Hi there,
i'm quite new to all of this, but i found this guy who has soem interesting info regarding grouding/coupling in designs.
Because you said any help is appreciated, maybe you're interested. Basically Hans Rosenberg has a 4 part yt lecture as a teaser to his free 9 part minicourse. His free minicourse is "Module 1" of his paid full course.
In his 4 part teaser he also throws in an example for digital signals