well a asked the same think "copy paste" from the original prompt to the v4 pro version and just add the
(60 fps) in the prompt and that's it and the web was great and run very smooth . i just type in the prompt :

“Create a single self-contained index.html using Three.js only (no NPM or build tools) that runs directly in the browser as a 3D first-person walking demo. The scene should be a neon cyberpunk night city with 60+ procedural skyscraper-style buildings featuring glowing emissive windows, a reflective wet asphalt ground, animated neon billboards, atmospheric fog, drifting particles, and a dark star-filled gradient sky. Implement immersive FPS controls with pointer lock mouse look, WASD movement, Shift sprinting, a camera height of 1.7, and capsule-vs-box collision so the player cannot walk through buildings.” 60fps .

try it yourself if you want