P1 and P2 both refer to table names that the census uses. They DO NOT refer to different "types" of projections.
In particular these projections refer to:
- P2: Population totals broken down by Hispanic or Latino, and not hispanic or latino by race
- P1: Population totals broken down by race
Attached are two documentation files where you can see the specific variables.
Source: https://www.census.gov/prod/cen2010/doc/pl94-171.pdf (page 43)