In the books I have read, it is not recommended to have two angels in a tank. But a dwarf and a full size angel are compatible. With that being said, I have seen two full size angels in a big tank. But I don't know how long they got along.
Queens are pretty dang territorial, even a 300 may not be enough room for french/queen combo. You may get away with a flagfin/french, however, I wouldn't try that. Better option would be a butterfly/angel mix. Some of the centropyges (esp. the pygmy angels) are only matched by 3spot, 3/4line damsels in their ability to terrorize a tank. 300 gallons does give you more flexibility if you provide plenty of hiding spots.
