Thinking back to when Kurama was still the Kyuubi it was a challenge for Naruto to go all out because of the threat of losing his mind. Now that it is known that you can transform with the karma seal, can this also be its downside? Right now he probably cant fully transform because the karma seal is not fully evolved. So he can only undergo a partial transformation like what Kawaki did. They're basically in the same boat except for a few major differences. The first is Kawaki's ninja tech body. I speculate that it was created to model the Juubi. This would give him a very strong constitution and massive chakra reserves but his mind could easily be corrupted if transformation means he would experience greater influence by whatever or whoever he is transforming into. His past would also play a large part in him being corrupted. On the other hand (no pun intended) Boruto is a royal branch Hyuuga of an Otsutsuki bloodline. Therefore he may naturally have better means to resist Momoshiki when the time comes. The first thing is that him being part Otsutsuki himself would allow the transformation to be more of his own form rather than Momoshiki's so the mental influence wont be as strong. Boruto has already defeated Momoshiki once so there is not only confidence but ability to reinforce that confidence. So while Kawaki may be more of a prodigy than Boruto he does not have the mental strength to resist Jigen. Boruto is different, he overwhelmed Momoshiki and forced him to pass the karma seal on to him. Boruto obtained the seal via triumph and victory. Kawaki obtained his seal because he was powerless to resist and this is the gap between them.