The short answer is that, YES! Page speed SEO is a real thing that affects each other. Google, and most search engines, consider speed as a ranking factor.
Now there are about 6 factors that affect SERP
- Keyword selection.
- Quality of content.
- Experience, expertise, authoritativeness, trustworthiness (EEAT)
- Backlinks.
- Site structure and design.
- User experience.
So if you're seeing good results understand that there is no penalty, per se, for having a slow website… but Google does favor faster sites in its search results. If the search engine is given the choice between two sites with similar factors, but one loads 2 seconds faster than the other, the faster site will always outrank it.
Now to your question about speed.
In short, your website should load as fast as possible! The ideal website load time for mobile sites is 1-2 seconds. 53% of mobile site visits are abandoned if pages take longer than 3 seconds to load. A 2-second delay in load time resulted in abandonment rates of up to 87%
This is the best page speed test directly from Google - shows below what is causing the delays but also the difference between mobile and desktop
https://pagespeed.web.dev/?utm_sourc...edium=redirect
Hope that helps and answers your questions