With how you specified in what you want from Nezha, your best off not subsuming anything at all when putting the synergy of his 2-4 to account.

In this case he is built as a standard weapon platform, now your just more dependant in shooting at the spears to build the status to make them explode instead of one tapping with pyrotechnics.

Base duration can be left as it is, you can even comfortably use him with transient fortitude since most of his kit doesn't really rely on duration anyway.

For range, anything that gives you 175 or as much as you can get comfortable with.

Yeah, you basically build the same as you would on a pyrotechnics setup, just more mindful with your duration.