My 1st level Wizard has a Wisdom of 13 (modifier +1) and proficiency in Wisdom saving throws, but not proficiency in Perception. Does that mean my passive Wisdom (Perception) score equals 10+1 or 10+1+2 (adding my proficiency bonus).
Proficiency in a Saving Throw is different from proficiency in a Skill
Each class gets a number of proficiencies.
For example, Wizards are proficient in both Intelligence and Wisdom Saving Throws and would add their Proficiency Bonus to any Saving Throws made with those attributes.
Wizards also have access to a number of skills like Arcana, Medicine, and Religion.
Having proficiency in a Saving Throw does not grant proficiency in a skill using the same attribute.
That makes your Passive Perception 10+1 = 11.
So, if a Wizard has proficiency with Wisdom Saving Throws, but not the Wisdom (Perception) skill, then any Perception skill-checks would not gain the proficiency bonus.