Elegant and Cool aren't their subpersonalities - those two columns are the animals' style preferences. Most likely determining which clothes they like (ex., when you give them a shirt and they go "this is exactly my style!").
The subpersonalities and what determine them has not been discovered yet, but there are research threads ongoing. The ACNH Official Guide confirms that there are 2 subpersonalities of each personality, but doesn't go into any more detail.
The information about interests is correct though! Each animal can have one of six interests, with some interests being more common for certain personalities. This determines how often you'll find them doing different activities around the island (singing, fishing, working out, etc) and definitely gives the villagers some more individuality.