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 (dvaita). It's understandable how the monist fusion of transcendental self and 'ultimate reality' can be criticised as a kind of solipsism, and it is a very ancient mode of criticism of Hindu thought. 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 emptiness, dependent origination, and inter-being. This should be understood as an emergent understanding of identity, as conditioned rather than defined by a unique essence, like the bundle-theory of identity developed in Western thought by Hume, and in relation to how identity appears but is not truly personal 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 and is a widespread school.
The Pureland schools of Jodo Shinshu and Jodo-shu focus on the '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?
Why is ontological relativism so hard to digest for many people (philosophers)?
Does there exist truly objective thoughts?