Completely replacing your drivetrain to save weight would be expensive. Dropping to 10 or 11 speed means a new shifter, cassette, derailleur. NX is one from bottom (SX is the lowest) level of SRAM's 12 speed options, meaning it is almost the heaviest.
Replacing the NX cassette with a GX or better starts dropping weight. If you have an NX drivetrain bike, you may have a heavy wheelset. You may also have an entry level fork, heavier fork. There are a lot of ways to drop weight, but they all cost money.
--Completely forgot that the NX is the HG driver, so scratch what I said.