- Is there a bright line / contours as to what constitutes practicing law?
For the most part, no.
There are some activities that clearly constitute the practice of law almost everywhere (e.g. representing someone in a court proceeding), and there are some activities that clearly do not constitute the practice of law almost anywhere (e.g. preparing your own tax return based upon your interpretation of the tax laws). There are many activities that are in gray areas and the definition varies from state to state.
For example, analyzing deeds to determine who is in title to real estate on a commercial basis is considered the practice of law in New York State, but not in Colorado.
- What are the elements ('litmus tests') to recognize practicing law
As applicable to the example in the question (there are an infinite number of possible situations so a full treatment is too broad), evaluating the law for purposes of guiding your own actions is generally not considered the practice of law.
An individual can represent themselves in any court proceeding to which they are a party (although usually they can't represent entities that they own) without practicing law.
Similarly, the Community Association Manager has to make one decision or another, and the law (outside of court proceedings) rarely requires that one hire a lawyer simply to make a decision that you are required to make in the course of your job. Consulting a lawyer increases the odds that the CAM will make the right decision, but interpreting the law as it applies to what you personally are required to do in carrying out your job responsibilities will very rarely constitute the practice of law.
On the other hand, if someone who was a former Community Association Manager held himself out as a "consultant" for current Community Association Managers, and in the course of that consultant work told Community Association Managers what the law required them to do, this would very likely be the practice of law, because it applies legal knowledge to particular facts for someone other than yourself.
The term "attorney" in its broadest definition means someone who takes action on behalf of another, and if someone is doing something on behalf of another, and it involves legal knowledge or a legal dispute, usually this will be found to constitute the practice of law.