Our typical user is a technician/engineer buying parts for a project of theirs. They usually order 20+ different items at a time. They use the website to generate a quote that their purchasing department can use to send us a purchase order. From there, things are processed manually.
An example would be a plumber coming to our website to pick parts for a project of theirs. They already have a good idea of what they need, they just need to be able efficiently navigate to all the different fittings, pipes, valves, etc.
About a decade ago, we made our own single page application to do this pretty quickly. Products can be added to the cart directly from the product category pages and the cart is visible and modifiable on any page of the website. No opening the product details page or navigating to a separate cart page is necessary. Unfortunately, that website is very outdated and is only good for this single purpose. It's not good for upselling or helping non-technical users.
I've noticed some platforms are pretty strict when it comes to the shopping experience. Navigate to category > navigate to product details > add to cart > get redirected to the cart page > navigate back to the store > repeat. That's fine if one t-shirt is being sold, but it's not fine for our business.
So, I'm looking for advice on a platform that would be a good fit for this sort of business. Something with an efficient shopping experience and the ability to turn a shopping cart into a formal quote.