The intention, when using a Greater Blood Talent is that the character choose two of the four options presented.
Those four options include the 3 racial talents, and the forth option is a stat adjustment.
In selecting 2 of those options, the player must replace 2 of his existing racial talents (his race's stat bonuses are NOT included on this side of the equation, they cannot be selected).
So for a Elf/Gryx hybrid, the player can select Lightning Reflexes, Dense Musculature, Night Vision, or stat bonuses (which include averaging the lifespan).
Once he selects 2 of those, he must then drop two of the following:Enhanced Senses, Quiet Stride, Night Vision.
His elven stat bonuses are not affected in any way unless the Greater Gryx Blood stat bonuses option was selected, in which case, they are combined (not averaged, but added).
If the stats option is not one of the ones selected, the hybrid will have a lifespan that is normal for his base race.
As for appearance -- yes, the Blood Talents should always influence appearance, but that also has nothing to do with the stats.