Yes (essentially)
Spells that give you a series of benefits don't generally care if you have overlapping effects. The only issue would be if the spell required a Size (which it does not, in this case). Partially combined effects simply do not stack.
Spells that provide bonuses or penalties on attack rolls, damage rolls, saving throws, and other attributes usually do not stack with themselves. More generally, two bonuses of the same type don’t stack even if they come from different spells (or from effects other than spells; see Bonus Types, above).
Same Effect More than Once in Different Strengths
In cases when two or more identical spells are operating in the same area or on the same target, but at different strengths, only the one with the highest strength applies.
One Effect Makes Another Irrelevant
Sometimes, one spell can render a later spell irrelevant. Both spells are still active, but one has rendered the other useless in some fashion.
You can have Frightful Aspect (FA) on with either/both of Enlarge Person/Righteous Might (only FA has the polymorph sub-school) and even cast it if you were naturally Large sized. But you will not grow further.* You will gain the largest size of the spell(s), the greatest Size Bonus to Strength, Constitution (etc), take the normal penalties for whichever size you end up, and still retain FA's DR, SR, and aura.
*Righteous Might/Enlarge Person will make you one size larger than you are typically, not one size larger than you were made by FA or another spell. So if you start at Medium, you would still only be Large if you have one of those and FA cast.
