Hi there,
think about the number of columns you want to display on your Archives. And decide upon the minimum width you want them displayed. A minimum column width should be around 320px as this is the average size of a Mobile display, and around a maximum of 360px.
For more columns use the smaller size eg.
3 x Post columns + 25% sidebar would be 4 x 320px = 1280px container width.
2 x Post Columns + 30% sidebar would be 3 x 360px = 1080px container width.
For the single post – the content width may be too large if you’re using those settings. But you can reduce the width using a Layout Element to say 960px for better reading widths.
To create a full width page you can use the Page Builder Container:
https://docs.generatepress.com/article/page-builder-container/