Netflix basic or standard?

Only I watch it alone.

Is the base quality really that much worse?

What would you take in my case?

What is more likely for you, what you are more satisfied with

Since you only watch alone, the basis would be most worthwhile. If you find out later that the quality is not enough for you, you can always change.

It depends on what you're watching Netflix through. The basic quality should be sufficient via a smartphone or tablet. However, if you have a huge TV, at least the standard subscription makes sense.

Can you change there at any time?

As far as I know, you can switch at any time.