• Google Analytics - enter a GA measurement ID; Sprwt loads Google's gtag script and configures Analytics (and Adwords if set). Use this if you only need Analytics.
• Google Tag Manager - enter a container ID (label: Google TagManager (GTM-XXX)); Sprwt inserts the Tag Manager snippet (script plus the no-script frame) so you can manage any number of tags from your GTM account.
• Google Tag - a field labelled Google Tag Only (without manager gtm) (G-XXXXXXX), intended as a standalone Google tag without Tag Manager.

In the current version this last field does not appear to do anything: the page code that would print the standalone tag script checks a different setting name than the one this field saves to, so the script is never actually inserted no matter what you enter here. If you don't use Tag Manager, use the Google Analytics card instead. All three fields live in Client Config under Marketing: Analytics.