How can I achieve responsive design for iPad, iPhone, Desktop, and Android?

I'm working on an assignment to develop a responsive UI for my company's SaaS application. We're using Figma, React, TailwindCSS, Next.js, and Jest. I want to ensure that the UI I build meets high-quality standards.

What tools or plugins have worked for you, or are you currently using to improve responsiveness and quality? I'm a beginner with just 1 year of experience, and I'm trying to level up my skills.

I'm currently using Pixefy, Resposively and the native options in Google Chrome and cross testing the behaviour in Webkit,Blink and Gecko.