Is the BPR8EIX the same as a BR8EIX?

Yes. BPR8EIX is the resistor version of BR8EIX, and the two are commonly cross-referenced. The P denotes a projected insulator tip. Check your engine's spec before swapping.

What engines does an 8 heat range suit?

NGK's 8 is a middle heat range, used on many motorcycles, scooters, karts and small two- and four-stroke engines. It is hotter than a 9 and colder than a 7, so match whatever the engine maker specifies.

Does an iridium plug add power?

Not on its own. The gain is a stronger, more consistent spark and longer service life than a standard plug. Any power difference comes from the engine and its tune, not the plug alone.

How often should it be replaced?

Iridium plugs typically last considerably longer than standard nickel plugs, but follow the engine maker's interval. Inspect the gap and electrode condition at each service.

What thread and hex size does it use?

It has a 14 mm thread and a 21 mm (13/16 in) hex, the common size for this plug family. Confirm reach and seating type against the plug you are removing.