We can measure how much data a remote needs to send in bytes. Basically each character in a string is one byte, so “ExampleRemoteKey” would send at least 16 bytes because it has 16 characters. When numbers are used, it needs to replicate a double which is 8 bytes long.
It’s a little more complicated than this though. Roblox also needs to send the value’s type as well as string lengths. There are cases where a string can use less data than a number, and there are cases where a number can use less data than a string. Here are some rough results using studio’s ‘Performance’ tab today:
Blank remote call: ~9 bytes
string (len 0): 2 bytes
string (len 1): 4 bytes
string (len 2): 8 bytes
string (len 3): 9 bytes
string (len 4): 10 bytes
string (len 5): 11 bytes
string (len 6): 12 bytes
string (len 8): 14 bytes
string (len 16): 22 bytes
string (len 32): 36 bytes
boolean: 2 bytes
number: 9 bytes
table (empty): 2 bytes
table (array with 4 numbers): 38 bytes
EnumItem: 4 bytes
Vector3: 13 bytes
CFrame (axis aligned): 14 bytes
CFrame (random rotation): 20 bytes