If I drop a Clustered Index, what will go off, and what will happen to Non Clustered Indexes?

If you drop the cluster index on the table, the table data will not gets deleted instead the offset table of the cluster index for maintaining the order of table data will gets removed from page, however since indexes use the clustering key to look up the corresponding row of data, so when a clustered index is dropped, the nonclustered indexes must be modified to use another method to lookup the corresponding data row because the clustering key no longer exists.

No for non cluster index the only way to jump directly to a record in the table without a clustered index is to use its physical location in the database (i.e., a particular record number on a particular data page in a particular data file, known as a row identifier—RID), and this physical location must be included in the nonclustered indexes now that the table is no longer clustered. So when a clustered index is dropped, all the nonclustered indexes must be rebuilt to use RIDs to look up the corresponding row within the heap.

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