I cannot definitively answer those questions, but my understanding is as follows:
If I sent someone as a beneficiary, are they a beneficiary of ALL an article's rewards?
I believe so. I am pretty sure beneficiaries get their set percentage of ALL tokens, e.g. Hive-related plus Hive-Engine tokens.
Does setting a beneficiary take from the author's rewards or TOTAL article rewards?
I believe it takes only the author's rewards. Curators get their full rewards regardless of how the beneficiaries are set.
If posting from a tribe-specific front end, does setting a beneficiary only affect that tribe token's awards?
In this instance, I believe the front-end would be adding a tribe-specific account to the beneficiary list for the post -- the beneficiary list is a Layer 1 feature. If that is what's happening, then the beneficiary would receive a portion of ALL tokens earned by the post, not just the ones associated with the front-end.
With all that said, I believe there is a Hive-Engine token config setting that enables setting up a beneficiary account that ONLY receives those specific H-E tokens.
So, if it is done via the front-end, it would apply to ALL tokens. If it is done via the H-E token config, then it would only apply to that specific Hive-Engine token.
@themarkymark, did I get the above correct?
Mostly yes. I went in depth answering these three questions here.
There are to facilities to be aware of. Hive beneficiary and Scotbot beneficiaries.
Hive beneficiaries are a blockchain level function and will split all tokens. It is used for Hive tokens but tribes will respect this setting. This can only be set by whatever tool you use to post. If you post on PeakD then PoB cannot enforce a Hive level beneficiary.
Scotbot beneficiaries will affect a single Hive Engine token regardless of where you post from. Scotbot beneficiary can be enforced regardless of which tool you use to post with.
In the case of POB which I talk about in my response linked above, the front end is enforcing a Hive beneficiary that takes 10% of all tokens. This in most cases higher than not using the front end and taking the 20% pob only beneficiary.
So, another question then is, what are we to do? How does this benefit the community if by using the POB frontend authors lose more money than if they don't.