Out of all the ecomm choices which is the most efficient to use, in terms of ordering management, speed, high number of products, wholesale options?
I'd also need to have something that allows customers to download images, shipping option that are work off the RRP price of a product etc
You'd need to produce a proper spec, or at least a set of requirements, then get someone to do the analysis for you and make recommendations; as no one can answer from this short detail; e.g. efficient to use in what way, to buy, to merchandise, to build, to maintain, what are the wholesale options for customers?
It's the same regards shipping that works off RRP, what does that mean; e.g. will shipping prices change by product RRP, will the service/carrier change by RRP, are you going to show different prices for different customers, how will this work, discounts by log in, voucher codes etc.
An ecommerce web project needs to have detailed requirements and an outline of how functionality needs to work for you and your customers, without this anything is a guess and projects like this are prone to massive cost/time overrun or failure if not planned properly.
You'll probably need several plugins to achieve this in WordPress/WooCommerce or custom PHP work, OpenCart will need PHP development based on your spec, the spec is key...