Quality Score:
90 - 100
50 - 89
0 - 49
*Source: PageSpeed Insights
*Example of Google PageSpeed Insights scoring.
SEO Score:
When attempting to optimize, an SEO score of 90 or higher is simple to achieve because this metric only measures basic on-page SEO factors (i.e. Title tag, Meta tags, ALT tags, etc).
Performance Score:
A high Performance score could be more difficult to achieve because it requires the webpage, files, and media to load efficiently.
If your website does not load efficiently, it can negatively affect the bounce rate, which in turn will decrease SEO.
Thus, it is important to consider your website platform. A light-weight html website is ideal for Page Speed.
However, for convenience and cost-effectiveness, most website owners opt for a Content Management System (CMS), such as WordPress, Drupal, etc.
This can be problematic for Page Speed, because CMS platforms typically use excessive overhead and unused code.
If you still prefer to use a CMS system, you should try out different templates to see which one(s) score well on Google PageSpeed Insights.