、。
A flawless plan feels stifling.
Literal
Fault [possessive-の] striking-place [subject-が] nonexistent plan [topic-は], suffocating [reflective-なあ].
非の打ち所がない is an idiom meaning 'flawless' or 'beyond reproach' — literally 'there is no place to strike fault at.' 窮屈 (stifling/cramped) usually describes physical tightness but here is figurative: the oppressive feeling of a plan that leaves no flexibility. The reflective なあ gives it a wistful, musing quality.