As far as I understand, any content related to finance or cryptocurrency is welcome. Adding on the tag when you post anything related to those couldn't hurt and if any of the curators think your content doesn't fit I'm sure they'd let you know. You don't have to post in their community, using their tag is good enough.

Their tag works similarly to neoxian, bilpcoin, palnet, et cetera. If you include it you can show up in their pages and earn that particular coin.

Ecency has a max tag limit of 10, I think hive.blog has a limit of 8.

If your post is about finance or cryptocurrency, you might as well add on the leofinance tag if you can. I don't really see much reason not to add it as you don't have to make any compromise unless you're already at your tag limit.