Anglican doctrine is based on Scripture, Reason, Tradition.
In Anglo-catholic worship, they put great emphasis on Holy Tradition (eg the teachings of the Early Church Fathers) and reject much of the Reformation.
The are not under the authority of the Pope, therefore are not Roman Catholic, but they do sympathise with much Catholic doctrine, such as Marian devotions, reservation of the Sacrament, rosaries, etc.
Anglo-Catholic does not mean High Church, as this term refers to worship style rather than doctrine. However, the vast majority of AC parishes will be High, simply because of their beliefs on tradition (so will have robed clergy, processions, sign of the cross, incense, etc.).
AC worship is often higher up the candle than RC.