update Rpath docs with diff btwn stringify, str

previously the docs did not indicate that stringify()
    would return the string representation of JSON strings
    while str() would copy JSON strings.

docs/RemesPath.md

@@ -618,7 +618,10 @@ x must contain only numbers. Booleans are fine.
 
 Returns the string representation (compressed, minimal whitespace, sort keys) of x.
 
-This differs from `str` in that *this is not vectorized.*
+When called with one argument, `stringify` differs from `str` in two regards:
+1. `stringify` is not vectorized.
+2. If `x` is a string, `str` returns a copy of `x`, but `stringify` returns the string representation of `x`.
+    * For example, `str(abc)` returns `"abc"`, but `stringify(abc)` returns `"\"abc\""`.
 
 *Added in [v5.5.0](/CHANGELOG.md#550---2023-08-13).*
 
@@ -1089,7 +1092,7 @@ Returns the upper-case form of x.
 ----
 `str(x: anything) -> string`
 
-Returns the string representation of x.
+Returns the string representation of `x`, unless `x` is a string, in which case it returns a copy of `x`.
 
 ---
 `zfill(x: anything, padToLen: int) -> string`