Tips and tricks for giving characters unique voices, plus ways to create your own languages!
How to Create thousands of Distinctly Different Voices (Vocabilities / Improve Your Voice)
EASY Voice Acting Techniques for RPG Characters (LunchBreakHeroes)
Player Roleplay with Taliesin Jaffe (Geek & Sundry / GM Tips with Satine Phoenix)
NPC Voices - define a single trait for an NPC that defines their speech patterns
Reddit ConLangs and its Discord server - quite in-depth studies and research for creating entire rules for how a language works