Shopify Website Redesign and Custom Portal

I want to redesign and modernize my existing Shopify website — cleaner layout, more custom branding, and an overall more premium look.
website is ROZNinc.com

The important part is this:

I do NOT want my entire website password protected.

I only want one separate portal page that is restricted-access for a small group of affiliate/wholesale customers (around 5–10% of users).

What I need for that portal:

A separate branded page/section
Password-protected access (or customer-login restricted)
Ability for me to add products manually
Different pricing from the public website
Tiered/bulk discount pricing depending on quantity purchased
Co-branding/custom branding for affiliate partners
The rest of the website should remain public and accessible normally

So the project has two parts:

Refresh and improve the visual design/layout of the main site
Build a private affiliate portal with custom pricing and restricted access

This should function more like a “members/partner portal” rather than locking the whole Shopify store. I dont want to manually tag customers, I want them to have access to the portal via a Password

If possible, I’d also like recommendations for the best Shopify apps or custom setup for:

tiered pricing
wholesale pricing
password/member access
affiliate-specific branding