Great points; we have top nav and it's never proved to be an issue. I'm working on a project where we've migrating from left to top nav and I anticipate issues because its a change for the user experience and we've already trained them on a different nav.

The goal should be the fewer clicks to get to the RIGHT item. (Which is subjective, for sure.) People will do more clicks to get to better data, however we shouldn't put them through any more clicks than needed - so, if you can do it in two, great, but if you need 3-4, then do 3-4.

The one thing I have noticed is that (depending on how big your site is) more clicks to get to deeper content can make it harder for search engines to get in and crawl those pages, which can reduce ranking opportunity.

Based on my conversations with Google, relevance is absolutely something to think about - if your site is all about oranges and you get links from sites/even blogs that are all about cars, it's  flag because it can look spammy.

Unless it's an outlier and is just one (or two) random links from sites that aren't related in content to yours, you risk harming yourself by connecting your site with unrelated content.

Actually, if you Google that (free online software that lets you create product catalog layouts) you'll get a lot of options. And that way you can better review what software or set up may be most compatible or easiest for you to use.