"High ranking official" and "top official" are similar phrases and can often be used interchangeably, but there are some subtle differences in their connotations. High Ranking Official: This term generally refers to an individual who holds a significant position within an organization, government, or institution. The emphasis here is on their rank or position within the hierarchy. A high-ranking official might not necessarily be the absolute highest authority but holds a prominent position. For example, a high-ranking military officer might be a general or admiral, but they might not be the top overall authority in the military. Top Official: This term typically refers to the individual who holds the highest position or authority within a specific organization or context. The emphasis here is on being at the very top of the hierarchy. The "top official" is often the ultimate decision-maker or leader in a given organization or government. For example, the President of a country or the CEO of a company is often referred to as the top official because they are at the pinnacle of power within their respective organizations. In summary, while the terms are similar, "high ranking official" can refer to someone in a prominent position within an organization but not necessarily the highest, while "top official" specifically denotes the highest-ranking individual or the person with the most authority in a given context.

They're basically the same. He met with high-ranking officials (or, top officials). 'High-ranking' is more general whereas 'top' is more like a superlative (maximum degree). 'Top' here just means occupying the highest levels of government, although, in some, cases, it could be a superlative...i.e. referring to a particular person with the highest rank in the system. But, you can basically use them interchangeably.