there's one in the resources tab i believe, although you have to do a lot of personalised tweaking to it if you want it to actually look good
to answer both of your questions:
Darkn spent a while customising his Livesplit and doing things in OBS, and in post, to make it look like that. I'm not sure personally since I don't run multi-level categories anymore. you'd have to ask in the speedrunning Discord.
https://www.speedrun.com/ultrakill/resources/ij9lr download the file here, and then download Livesplit. head into Livesplit and import the file as a template. from there you can edit the name of the splits, the way it looks, etc.
If you want to customize it further, or do something specific, i'd recommend asking in the speedrunning Discord. that'd be your best bet for support on this stuff ^^
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