Is the TR6IX a direct replacement for my current plug?

Only if your engine calls for this heat range and thread. Check your owner's manual or tuner's recommendation for the correct NGK stock number before fitting.

How is it different from a platinum plug?

The iridium center electrode is harder and has a higher melting point, so it is built for longer life and better ignitability in demanding engines.

Do I need to gap it before installing?

NGK sets the gap at the factory. Check it against your engine spec and adjust carefully, since the fine iridium tip is fragile.

How many plugs come in one order?

This is a single plug. Most four-cylinder engines need four, so order the quantity your engine requires.

Is it worth it over a standard copper plug?

For tuned, turbo or high-revving engines, the longer life and fouling resistance justify it. For a stock daily driver, a standard plug is often enough.