Hello 
It is not a full-text search anymore, it’s a basic search “%mysearch%” done on all fields (except relational ones)
Doing a search on relational fields can lead to performance issues so I recommand to use a search provider like algolia or elastic seach.
However, if you want to implement a search only for onts and only for some of its relations:
- I believe you can make differents search for each model (onts, address_unit, services…) but I would not recommand it
- Or you can write your own custom raw SQL query (or mongo query) as described here : https://strapi.io/documentation/v3.x/concepts/queries.html#custom-queries so you can optimize it to your needs.
I hope it helps !