I don't know why this topic keeps coming up. I think it's because these are used as methods of attack against Buddhist thought.
Buddha taught 'the middle way', between eternalism and nihilism, between an unchanging transcendental soul/identity/essence, and nothing continuing after death - this is typically translated into English as nihilism, though it doesn't conform entirely to the philosophical term. It's from two millennia before, and an entirely different culture so it's no great surprise! The idea Buddhism is nihilist in modern terms of moral nihilism or existential nihilism, are total non-starters. The morality and meaning-cosmology of Buddhist thought are highly developed, although the emphasis on return to your personal situation right now, in priority over any elaborations, can be related to a very specific understanding of nihilism as meaning and purpose never being truly external, absolute, and real outside our own personal experience.
Hindu thought is generally monist, and either non-dualist (advaita) or dualist (advaita). It's understandable how this can criticised as a kind of solipsism, and it us a very ancient mode of criticism. Discussed here: Different between Buddhism and Solipsism
Buddhist thought deconstructs conventional notions of the self. If there is no unchanging self, how can there be solipsism? Buddhism emphasises sunyata, also called dependent origination, and inter-being. This should be understood as an emergent understanding of identity, like bundle-theory of Hume, and is best illustrated by the ancient metaphor of Indra's Net.
It's worth saying Nchiren Buddhism dismisses previous Buddhist thought, and places Nchiren himself over other authorities, so I wouldn't consider it 'mainstream Buddhism', even though it shares many outward practices.
The Pureland schools of Jodo Shinshu Jodo-shu focus on other-power of Amithaba, instead of self-arising awakening of traditional Zen (Soto & Rinzai). Happy to go into more detail of schools or doctrines if you have further questions.
How is the concept of "beyond word" viewed in many school of thoughts?
What are some good resources for learning Indian philosophy?
Is there anyway to prove things happen/exist if I'm not aware of them?
What are the problems in ontological relativism?
Does there exist truly objective thoughts?