Is the phrase 'top-level' appropriate to describe data that makes general obeservations as opposed to more detailed ones?

I suggest "high level" instead. Here's the relevant definition from the OED:

[...] relating to or concerned with a subject, system, or phenomenon as a whole, rather than its particular details.

Here's the OED's only definition for "top level":

The highest degree of importance, prestige, or ability; usually (with hyphen) attributive, designating that which belongs to or takes place at such a level.

I'm a data scientist and, depending on the situation, I might also refer to "summary statistics" or "metadata." If you provide a sample sentence, it would be easier to pick the right word.

Related to comment of @FumbleFingers. How about summary data? From Lexico:

summary: Not including needless details or formalities; brief. E.g., summary financial statements.

Summary financial statements provide a good example of presenting "general data in the form of statistics or reports that give somebody a general overview on a topic" as distinguished from "very specific and nuanced insights and findings one may take from a specialist report."

COVID-19 data for number of cases and number of deaths provide another good example. One could have summary data for the world as a whole, for individual countries, for collections of countries, for parts of individual countries, etc. One could also break the data down by age, race, socioeconomic factors, etc. You would have to decide what to include, or not, in your summary data. Specialists and other interested parties could "drill down" to any level of detail desired in more detailed reports.