As a full-stack developer and an extensive knowledge in WordPress and its ecosystem for over 10 years, I am confident I am the ideal candidate for your sophisticated user login and registration form project. From the description provided, it's clear that you require extensive customization, specialty in custom fields and design elements - and I can deliver just that. Throughout my career, I have demonstrated customizing WordPress themes and plugins to meet unique needs like yours.
In addition to my proficiency in HTML, CSS, JavaScript, and responsive design - which will ensure a visually appealing and functional outcome across all platforms - I also bring valuable user interface design experience to the table. This guarantees not only a design that fits your brand precisely but also enhances users' experience.
Lastly, given the nature of your requirements including possible need for custom plugin development, my skills in ReactJs, Nextjs, Strapi, NodeJs, Vue js, AngularJs, MongoDB, ExpressJs etc would be extremely beneficial. With all these said, if chosen for this project not only will i ensure timely delivery with a stringent policy on deadlines but also guarantee my undivided attention to create a secure websites that remains efficient suiting all your needs. Choose me today let me bring your vision into reality. Looking forward to discussing further with you!