If you think that ReachDeck is in any way slowing down the loading time of your site we would recommend placing the toolbar at the bottom of the body just before the closing tag, then ReachDeck will wait until your page has loaded before starting to load the Toolbar.
It will not affect your content from loading. We also utilise cache, so after the first time you load, most of these files will be loaded from your browser's local cache, because we utilise lazy loading to minimise the file sizes, we only load components as and when needed.
It has been noted that some metric tools such as "GTMetrics" or "WordPress Performance" do not understand the ReachDeck plugin and are returning negative results. The ReachDeck toolbar must wait until the page has fully rendered before it can begin loading, which is why it may appear to be slowing the loading time of your site. Although ReachDeck loads after your content, it does not impact the users ability to interact with your page before it has fully-loaded.