I see where you are coming from, and I do not have a good answer then, when I did a lowercase redirect I started by creating the new lowercase pages then setting canonical to them.  After a few months I removed the uppercase versions and redirected them to the new lowercase.

Another quick fix would be to use a canonical tag on all of your pages pointing to the full lowercase versions.

So for the URLs example.com/UPPER; example.com/Upper; and example.com/upper you would place the following into the head so Google knows that these are just variations of the same page, and if will point search to the desired page example.com/upper

https://support.google.com/webmasters/answer/139066?hl=en

With the new version of Google Analytics and GTM, you no longer code referral exclusions into the ga.js, instead you should be excluding them in the admin section.

https://developers.google.com/analytics/devguides/collection/upgrade/reference/gtm