can Business Catalyst product catalogs be used to set up parametric searches?
re: tags and product parameters list seperate from the description.
can Business Catalyst search module do parametric searches?
Don't think so, I don't think (correct me if I am wrong) there is a way to search tags.
If you could search tags what you would do is run fire of three searches (tags, product parameters, general) at the same time once the user press' search) using AJAX, wait for the reply from all three and display it how you would want to display them.