Is it permissible for a Muslim who does not adhere to a specific madhhab to choose from the four madhhabs what is easier for them in matters of worship, such as choosing the ruling on clearing the throat during prayer based on the opinion of a madhhab that permits it?

The disagreement among scholars is a mercy, and their consensus is a proof. A layperson is not obligated to follow a specific scholar; rather, their madhhab (definition) is the madhhab of the one who gives them a fatwa (definition). All the Imams of Sunnah (definition) are on true guidance.

Clearing the throat (al-tanahhuh) during prayer is permissible if it is due to a need, an overwhelming urge, or a ضرر (harm/necessity). It is disliked if its purpose is to convey understanding, according to the Maliki and Hanbali schools. There is no harm in adopting the view of Imam Ahmad or others on this matter, as long as the intention is not to seek out concessions (tadayyu' al-rukhas).