will anchor "mybrand keyphrase" get me same results for the keyphrase target as using just "keyphrase" as anchor?
Yes, it will "help" you get that keyword pending your competition isn't killing you in backlinks for that keyphrase.
right sure it will help BUT more or less ie "mybrand KEYPHRASE" OR JUST "KEYPHRASE" as the anchor will help target the KEYPHRASE
Well, if you can - mix it up. Use BOTH of them. This will be considered by the search engines to be "more natural". If they are all just one, then you have something of a "signature" which is typical of an affiliate marketer, and the search engines seem to not like affiliate marketers. Hope this helps, InternetMarketing108