You have chosen a complicated topic.
Symbols and objects are important aspects of Catholic worship and private devotions.
But the Church approaches this on two levels. The first are the seven Sacraments (Baptism, Eucharist, Reconciliation, Unction, Matrimony, Confirmation, and Holy Orders). The Church defines a “sacrament” as an outward and visible sign of an inward and spiritual grace. In other words, something is objectively happening as a result of the rite alone. It does not depend on our belief or faith - bread becomes the Body of Christ no matter what you or I believe about it.
Every Sacrament has five components which must all be validly present: recipient, minister, form (the words used), matter, and intent (of the minister). The result of the Sacrament is a form of divine Grace called Actual Grace. The effect of Grace is to confirm and enrich us spiritually. A Sacrament would not ordinarily have a scientifically testable outcome (and, if that happened, it would be considered miraculous).
Then there are sacramentals. Although the name is similar to Sacrament, these are very different. Examples of sacramentals include rosaries, crucifixes, holy cards, vestments, holy water, and funerals.
The Church does not teach that sacramentals confer grace. That would be considered “magic” by the Church. Sacramentals serve to focus our attention and prayer, which can (and will) result in Grace, but not because of anything to do with the sacramental. You don’t get “extra Grace” simply because you’re holding a Rosary.
Sacraments are important (and Baptism is necessary), but the Church does not compel anyone to make use of sacramentals. These are always optional.
There has been much superstition over the centuries regarding sacramentals, and there still is, to some degree. Some people wear brown scapulars like
this one with the so-called Sabbatine Privilege printed on them (it’s phony, obviously). It is superstition to think that wearing a bit of wool will assure your salvation, though you will be in good shape if you strive to live by the Carmelite values the scapular represents.
The Church believes that we can impact God through our prayers, but we cannot control him. The faithful Christian prays as Our Lord did in the Garden: “thy will, not mine, be done.”