difference in greater and perfect currency

lets say greater exalt and perfect exalt does perfect exalt have bigger chance at getting t1 mod? it says on it minimum modifier level 50 does that mean if theres only lets say 2 more modifiers after level 50 that would mean its 1 in 3 chance for perfect exalt to hit t1 mod? and if greater exalt min mod is level 35 and lets say its 4 modifiers after level 35 that means with greater exalt its 1 in 4 chance to hit t1 mod?

correct, in most cases perfect ex culls one extra mod compared to greater.
depending on the mod you could still get a t4 even with perfect.