If you clean up your PC it's unlikely to improve its 'performance', as that word is generally used, for example in a benchmark. What it might do is make it start up quicker, be more reliable, and easier to maintain - all if which is 'performance' of a sort in that you waste less time. To make it quicker add more memory (less disk access), fit an SSD (quicker disk access) or a faster processor (generally impracticable on a laptop).

On the last point, the performance of a given application - a spreadsheet say, or a browser - is not much affected by what operating system it runs under. One OS may be easier to use, quicker to load, offer nore features, or be prettier than another, but once you load and run your application there's not much difference.