if bob the ranger has favored enemy +2 (orc) and favored terrain +2 (forest), does he get +4 to perception and survival checks against orcs in forests? they are unnamed bonuses, after all.
Untyped bonuses from different sources? It doesn't get more stackable than that.
so a 20th level ranger with favored enemy +10 (orc) and favored terrain +8 (forest) gets +18 to perception and survival checks against orcs in forests.
Yes, and a 20th level wizard and scry out the location of the orc, his family, his dog, and his dog's family, and then summon and bind angels to smite them all. Don't get too impressed by a double digit skill buff on a 20th level character.