I felt like I needed to do this since I have so many more characters XD
 
T:  
Larger than most stallions and ponies in general for obvious reasons. He inherited a lot of dragon genes that made him much bigger
 
Illusion:  
He’s taller than most ponies since he is the son of Celestia (who is quite tall) and Discord (who is very long). Illusion is not much shorter than T, but his is smaller. He is very skinny and lanky
 
Valiant:  
He and Illusion are generally the same size. Valiant, however, is more bulky and muscular.
 
Del:  
Del is the size of his uncle Big Mac and is just as muscular
 
Crme:  
She is around Del’s height. She is very tall for a mare and very slender
 
Prism:  
He’s the shortest of the guys and the average size for a stallion. He doesn’t mind since pegasi benefit from being small when flying
 
Claire:  
Claire is just about as tall as Prism (arguably taller due to her horns). She is also rather tall for a mare because of her dragon genes
 
Red June:  
June is slightly shorty than Claire but is much thicker and muscular which is no surprise since her father is Big Mac
 
Nidra:  
Nidra is rather small for an alicorn as she is still very young
 
Anthea:  
Annie is slightly taller than the average mare (she’s all legs). This is primarily because her father is a very tall stallion
 
Whirlwind:  
Whirlwind is almost as tall as Annie but seems her height just because of her mane.
 
Candy:  
Candy is the size of the average mare
 
Starburst:  
She’s tiny. But her large wings make up for it
 
Icy Storm:  
Icy is almost around Star’s height.
 
Pixel Bit:  
She’s tall for a filly. Pretty lanky and awkward
 
Nighty, Echo, Cloudy, Sugar:  
They are all the average size for their gender and age
 
Api:  
Api is VERY small. She seemingly didn’t grow at all since she was 5