In LOR proficiencies are independent for each category and folllow 5 tiers.
Proficiency Tier and Proficiency Tier Modifier
Each core proficiency and skill has a proficiency tier assigned to it. When LOR calls for a proficiency tier modifier, it refers to the modifier that your proficiency has.
Tier | Proficiency Tier Modifier
Untrained | 0
Trained | +2
Expert | +5
Master | +8
Legendary | +12
Proficiency Modifier
Proficiency modifier is what is assigned calculating modifiers and bonus. It is the default bonus that skill has unless stated otherwise.
It is calculated by this formula if it is of a Trained proficienct tier are higher. If it is not trained, the value is 0.
Half Level (Round up) + Proficiency Tier Modifier
Final Calculated Modifier
After calculating the modifier, you add the relevant ability score modifier that is used for that core proficiency. Be it Strength, Dexterity.
Thus:
Proficiency Modifier + Used Ability Score
This is the modifier you use to determine the usage of the skill or core proficiency.