Rune Knight's Giant's Might states:
If you are smaller than Large, you become Large, along with anything you are wearing.
(Note: I am linking to the UA because it is freely available and has the same wording for the feature related to this question.)
The spell Enlarge/Reduce states:
Enlarge. The target's size doubles in all dimensions, and its weight is multiplied by eight. This growth increases its size by one category - from Medium to Large, for example.
Is it simply a matter of order of operations? Interpretation A:
- A Hill Dwarf Rune Knight activates Giant's Might, causing his size to become Large.
- His ally casts Enlarge/Reduce on him, using the Enlarge Option, causing his size to become Huge.
As opposed to inverting the order:
- Enlarge/Reduce causing his size to become Large.
- Giant's Might, causing his size to not change.
Or does one feature override the other resulting in Interpretation B, due to Specific Beats General:
- Giant's Might, causing his size to become Large.
- Enlarge/Reduce, causing his size to not change, because Giant's Might forces it to be Large.