I agree with the topic of nylon being criticized as an outdated topic. People used to say not to use poly either. However all thread have changed over the years and improved drastically and people who have had bad experiences with older thread continue these myths about thread. High quality brand you should be okay. I would get a sample of both the nylon and monopoly and see which you like better and works better in your machine. I have use both monopoly in top and bobbin successfully. Many also like to use superiors bottomline in the bobbin with the monopoly so you might want to try that. As for invisible thread most of my instructors on craftsy either use the YLI or superiors Monopoly in their quilts all the time for SITD with no issues. those are the 2 brands most highly recommended.