lighting makes no difference to the fishless cycle, temperature can make a difference.
add ornaments - yes.
add plants - maybe: depending on what level of ammonia you are using, the ammonia may be harmful to some plants in high concentrations. If you are concerned about your plants, you can add a lower amount of ammonia, or wait to add plants until your cycle is complete. Another option is what's called a "silent cycle", where you plant ~30% of your tank by volume, give your plants a few weeks to establish themselves, and then do a fish-in cycle with the plants there (which if all goes well will result in no ammonia or nitrites registering because your plants will consume them as they are produced).
this has more details:
https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/