CSS Flex & Grid Layout Conversion

I'm looking to convert a mock-up CSS to use Flex and Grid layouts. The goal is to maintain the exact look and ensure responsiveness across various screen sizes (14/16-inch laptops, 27-inch monitors, and others).

Requirements:
- Use provided mock-ups and existing CSS + HTML for the 14-inch laptop as a base
- Replace hardcoded px values
- Ensure main content area remains visually identical across all screens
- Optimize for 16-inch laptops, 27-inch monitors, and additional screen sizes
- Use MIT or Apache licensed CSS frameworks/libraries if necessary (Bootstrap, Tailwind CSS, etc.)


Ideal Skills and Experience:
- Proficient in CSS, Flexbox, and CSS Grid
- Strong experience with responsive design
- Familiarity with adapting existing codebases
- Background in working with popular CSS frameworks

Quotes needed per UI screen.