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Thank you very much Ruth.

Ideally, I'd ask to see examples of the companies' work within these platforms for other clients. I agree with Prestashop that many companies have made many different platforms work for them in a variety of ways. Modern platforms are usually not too bad for SEO no matter what you go with, but all have their particular issues. I would not worry too much about keywords further down the URL structure; there are many more important factors for best SEO practice, and it's possible / likely that this is not an issue at all anymore. Where the ecommerce platform is hosted also should not be an issue. The quality of site they can produce within these platforms would be my concern, and it's possible that a company with a "less desirable" platform can actually produce something that is of an overall higher quality, including when it comes to SEO. I'd definitely seek as many case studies / examples as possible.

Thank you very much.

I think there's no way to get a real answer. Think of this. Let's say Microsoft.com wants to rank for Debt Consolidation as a keyword which has a keyword difficulty of let's say 75. Another keyword they want to rank for is Software, which lets say is 95. Considering their domain content niche, the nature and relevancy of the links pointing to Microsoft, which would essentially be related to Software, it would be very easy for that domain to rank for Software then Debt Consolidation even though Debt Consolidation might be a lot easier in terms of keyword difficulty. I would read the keyword difficulty in terms of what kind of keywords you currently rank for, the keywords you want to rank for, search volume and the niche of your website to figure out which keywords you should be targeting. I hope that makes sense.