No, NPS Tier 2 funds don't have any investment cap. There is also no minimum account balance and no lock-in period or exit penalties. You also do not get the tax benefits unless you are a government employee. They work very much like a Mutual Fund.
Government employees in India get Rs 1.5L under Section 80C. But their investment comes at 3 years lock-in period.
NRIs are not permitted to invest in the Tier 2 Funds of NPS.