Working with multiple clients is possible because design (as in, actually drawing rectangles in Figma or Framer) is part of a larger process

— brief / feedback
— gather inspiration
— gather materials
— design

Then you deliver, get feedback and iterate or move to the next piece

The size / complexity of each deliverable can vary, but it should not be too simple or too complex: if it's too small (eg. a button component), you'll be arguing the sex of angels; it's your job as a designer to make these smaller choices in a way that fits the larger vision

But if it's too big, giving feedback (and having buy-in from relevant stakeholders) becomes very hard and revisions more likely. I can make an entire website in a day, but I'll make it the way I like it

What you want to do is measure twice, cut once. Divide complex task in smaller, intelligible deliverables: moodboard, prototype, lo-fi, hi-fi. Get buy-in at every step of the way

Thus everyone lives happily ever after

The end