Is this a good method to use while trying out a lot of ideas? Usually when I am optimizing code, most of the ideas don't work out and performance remains roughly the same (or so I think - I don't really know and want a better workflow here).

But if you do this test repeatedly, even if the code had identical performance, you'll get a false positive 5% of the time. And depending on the spread of the timings you might not get a clear XXXYYY win even when it is indeed a minor improvement.