This is more of a design question - not just a coding question.
I already have an app that stores data in SQLite DB tables. Now I want to add Search feature into thi
FTS tables cannot be efficiently queried for non-FTS searches, so option 1 is out.
The entire FTS table essentially is an index. This is a speed/space tradeoff, and the ability to do full-text searches usually is worth it. To avoid storing the original text twice, use external content tables.
To keep the original and FTS tables in sync, use triggers.