I think you have to know your madreigah.
If you have true bitachon that you’ll have the money for whatever you need, then I would say that is enough. But I think that’s a very high level of Bitachon and most people would instead convince themselves that they have bitachon rather than actually having it.
I don’t think that there is any reason to connect the Hebrew word “bitachon” and the loshon hakodesh word “bitachon”. But that being said, when I got married and needed to get insurance, my Rebbe didn’t tell me to get the best that I could afford, just a basic regular insurance.
When it comes to Bitachon, there’s no “one size fits all”. Everyone needs to dicuss with their Rov the level of bitachon that they have and how much of an impact that bitachon should have on their cheshbonos.