different sidebars on each page

Hi, in Customizer you can choose the layout of each page or post when you edit it : left, right, left and right or no sidebars.
In appearance > widgets, you can decide which widgets you’ll want to display in each sidebar : left or right, for the entire website.

Now your point : you need to apply some widgets here and not there.

To do that, you’ll want to use a plugin like widget logic which does this job very well. It uses the conditional tags syntax which you can be familiar with in 2 minutes.

Hope this helps!