Nikko: Private or public transport?

Hi all,
I'm hoping someone can answer a few of my questions - much appreciated!

I'm planning on doing a 1-day trip from Tokyo to Nikko. (Between the 2nd of Dec to 5th Dec or on the 25th November) Unfortunately, my schedule doesn't allow me to visit earlier in the peak season.

I'm looking to cover via a mix of public transportation and walking:

Kegon falls,
Lake Chuzenj (will skip Chuzenji temple),
Ryuzu falls,
Senjohara Plateau
Yudaki falls
Shinkyo bridge
Narabi Jizo (if enough time to squeeze in)

1. Should I consider private transport instead?
2. Is 1 day enough to cover all of this?
3. Should I prepare for snow/wet tracks?
4. I've heard there's been an increase in bear sightings in Nikko, do I need to bring a bear spray?

I'm more of a beginner at hiking so hoping it won't be that isolated at this time.
Thanks all!

The spots you want to visit are concentrated on the bus route, so you may be able to go if you want to. The sun sets early in November and December (between 16:00 and 17:00), so it is recommended to go first to Senjoga-hara and Ryuzu Falls, where there is likely to be no light.
Currently, only the bus schedule until November is announced.
https://www.tobu-bus.com/pc/area/pdf/nikko_timetablenatsu.pdf?2024
December will probably have fewer buses.
Senjoga-hara seems to be closer to Aka-numa bus station.
https://www.andtrip.jp/article/004339.html
Nikko bear information
http://www.nikkoyumoto-vc.com/nature/kuma_d.html
You may also want to take a bell to ward off bears.
Please refer to how to deal with bears.
https://www.nhk.or.jp/radio/magazine/article/yamacafe/xJD5Ogznk.html
On average, it seems that snow piles up in Oku-Nikko from around November 30.
https://www.data.jma.go.jp/obd/stats/etrn/view/nml_sfc_season.php?prec...
last year's information
http://www.nikkoyumoto-vc.com/new/nature_d.html?0:3034
http://www.nikkoyumoto-vc.com/new/nature_d.html?0:3035
http://www.nikkoyumoto-vc.com/new/oshirase_d.html?0:3037
http://www.nikkoyumoto-vc.com/new/nature_d.html?0:3044

You forgot to go to Yutaki too.
Yutaki seems to be close to the Yutaki iriguchi（湯滝入口） bus stop number 44.
https://www.nikko-kankou.org/spot/115
The toilets will be closed from early December to April.
The rest house will be closed from mid-November.
http://www.yutaki.com/

By the way, the area around Shinkyo Bridge will be lit up from November 29th (Fri) to December 1st (Sun).
https://www.tochigiji.or.jp/event/e15094
Shinkyo Bridge seems to be always lit up.
https://www.nikko-kankou.org/spot/21
Kegon Waterfall will be lit up from November 16th (Sat) to November 24th (Sun).
https://www.tochigiji.or.jp/event/e15115/
Kegon Waterfall is fine if you only see it from above, but if you want to see it from below, please pay attention to the opening hours of the elevator.
https://www.kegon.jp/info/

Thank you so much for the information @haro1210 - based on it, I'm thinking of going to Nikko on the 25th of November instead of December (because of the fewer buses). Do you know how populated it will be at this time?

I hope to start early and hike through the marshlands, see Yutaki falls on the way to Yumoto onsen. Afterward, I'll look to take a bus back to Narabi Jizo and then walk to Shinkyo Bridge. Does this seem reasonable for a 1 day trip?

Number of tourists in Nikko last year
https://www.city.nikko.lg.jp/material/files/group/25/kankoutoukei2023....
I think you can enjoy even one day, but I recommend staying one night if possible.
Especially, if you haven't been to Toshogu for sightseeing, I recommend you to go there.