I've nicked this bit from the interweb: Something that is practicable is something that can be reasonably done. Look at the word within the word, practice, plus the suffix -able, and you have something that is able to be put into practice, or practicable.
I consider the difference between 'practicable' and 'possible' like this. Following an engine failure, if the checklist says 'as soon as practicable' you will go somewhere 'sensible' - which makes it a judgement call. 'As soon as possible' means something different. It means land at very first airport you can land at: ignoring access, handling, engineering, RFF, medical back-up etc.
Competence (or competency) should describe the ability of an individual to do a job properly. However, the low-life in Human Remains tend to use it to describe attributes required for a job (or are they now called "pivotal roles within a dynamic environment"?) with and other such bunkum. But as I'm unlikely to ever apply for another job they can shove terms like this where they keep their common sense.
PM