I live alone and I basically use one device at a time to stream or to browse or for other reasons to be online. Believe me, 300MBPS is plenty. My provider is Optimum and I have 100 MBPS service I find quite adequate for me to stream Netflix or Amazon Prime or YouTube.
One reason to get 500MBPS would be for a family to have so every person could be actively online or streaming simultaneously. You do not meet that criterion.
Please be assured there is no advantage to you to
spend $25 more per month, $300 more a year, for bigger bandwidth.
Choose 300 MBPS with confidence. It's very easy to upgrade if you find any negatives.