How Does Stackable Affect My Page Loading Speed?
Stackable shouldn't affect your page loading speeds much since the vast majority of Stackable blocks do not require any server-side PHP processing in order to get shown in the frontend.
Aside from this, Stackable usually just loads a handful of Javascript and CSS files in the frontend. These files when compressed total at around 30kb~ only. These files do not change across your website so your visitor's browser can easily cache these files.