When Boruto was practicing to enhance his skill in episode 16x Kakashi mentioned that he can't create Odama Rasengan because he has low Chakra reserved. Likewise, several previous episodes also mentioned that he cant create even more than 10 Shadow Clone.
Kakashi explained that Naruto can do it because he is a Jinjuriki. Now, that is a bit contradicting since Konohamaru can actually do Odama and Taju as seen in episode of chunin exam between Konohamaru and Naruto.
So, why can't Boruto use Odama Rasengan & Taju Kage Bunshin? But Konohamaru can.