There are other steps you can do to check for variable FPS drops. I maintain a guide with most of these recommendations here in the technical support forum:
[Maximizing System Performance for Overwatch PC]
by WyomingMyst
Welcome to the Maximize Overwatch Performance guide! Here you will find various tips and tricks that help users get every possible frame per second, the lowest possible simulation rate, and minimize spikes of system lag during matches of Overwatch. This guide will go over recommended settings in Overwatch, settings outside of Overwatch, and other tricks you can use to improve performance. Please note, this guide is intended to i…