I really don’t think I can give any good advice without having something more to go on. Show me something you have now and I can give you some feedback.
It sounds more like “Writer’s block”. You just have to start coding. You won’t ever have it all in your head in some perfect state before you start. You will re-factor code along the way, re-structure the HTML, renaming classes, doing some CSS one way and then changing it later. It is an iterative process and the most important step in that process is just starting (showing up is half the battle).
Angular and Bootstrap are two completely different things. Bootstrap is a CSS framework that lets you write less CSS and maintain some visual consistency. Angular is a full-fledged application framework and is much more complex and harder to learn. It should be used to solve a specific problem. Not used, just to use it.