In my testing it hasn’t caused any noticeable impact. In theory it could cause a very slight performance hit on the Sidekiq process. The impact should be fairly minimal because the logging disk i/o is performed in a separate thread, allowing other things to continue in the main worker thread.
Each JSON object is on its own line, so you can simply do something like
cat sidekiq.log | grep pending
And then parse the JSON that you get out of that.