It depends on the brand. Some clothing brands don't have a 2T. My son is 13 months and is in 2T or 3T. Both are pretty long on him but fit around his waist. The shirts fit him 100% eithout being to big
2T is slightly bigger than 24 months if you prefer a looser fit i would go for the 3T. Then again it depends on the brand too
My son is 4 and is in size 6/7 (small) in the big kid section for shirts but still semi fit in 5T bottoms. My nephew is 1 year old in 5T clothing. He’s a chunky baby though.
My son is 14 months and is in 3T & 4T. He's also little chunky, so I like to go up a size, especially depending on the brand.
2T is longer and leaner compared to 24 months. I’d try 2T, if still doesn’t fit… yes 3T.