Hello @martin136
The cache is disable by default, because WordPress is an ecosystem with many plugins and themes of different developers, and I cannot ensure the form be cached properly in all scenarios. So, you can enable the forms cache, and check if it is working properly for you.
Concerning to the big difference between to use the forms cache or not. Enabling this feature, the fields tags are included directly in the page’s content with server side code, if the feature is disabled, the HTML structure is generated with client side code when the DOM be ready.
Best regards.