there's different meowing sounds, meaning different things - at least when not accompanied by any emoji or context saying otherwise
"mew" is for a "I don't feel well"
"meow" is a random meow sound - gimme attention, meow back, give headpats, whatever
"mrew" is a meow with a purring sound in it - I'm excited about something
"mrrrrew" is an even more excited "mrew" - it scales with more r's!