For new Google Ads conversions without customization, click-through defaults to 30 days and view-through to one day. Available options vary by conversion source and type, so inspect the individual action.
It is inaccurate to say one Google Ads setting controls all GA4 key-event counting and attribution. Distinguish linked-conversion management from the attribution settings for key events.
Choose based on observed decision timing and measurement purpose, not a universal industry recommendation. Google Ads window changes apply going forward; record the date and values for comparisons.