There is no reason you could not lamp this unit with a bulb with less wattage so long as it is the right shape and size — and since the part numbers are listed on the back those are clearly the bulbs to buy.
Yes, hang onto that 2K bulb. You never know when you’ll need it.
When changing bulbs, be sure to NEVER touch any with your bare hands — your fingers will leave miniscule oil traces on the bulb which will shorten the life of the bulb substantially. Always use a clean cloth or clean gloves or a piece of kleenex. (And let the bulb cool down before touching….)
If you are unclear about color temp, learn about that by searching this site and also Google. Kelvin color temperature refers to one of two color axes you need to pay attention to, the red-blue axis. The other is the magenta-green. The significance of these and how to correct has been explained several times on this forum.
Rick Wise
director of photography
San Francisco Bay Area
and part-time instructor lighting and camera
grad school, SF Academy of Art University/Film and Video
https://www.RickWiseDP.com
https://www.linkedin.com/in/rwise
email: Rick@RickWiseDP.com