User agents have to be the newest browsers, if you use an old one, they start not counting your votes prior to banning.
You will need an IPV4 space as they treat IPV6 as spam right now. 100K bots means at least 80,000 ip addresses.
They track login times across accounts which vote on a similar item, or it may not be login, but, it may be action time, so your cron jobs have to stagger.
The best way to do it, is pay people in third world countries to legitimately post. It was about $1 per person, per day to post 2 times. We would pay them once a month and it was insanely cheap. The issue is then Reddit started banning on geo location so now you need people in poor countries who have a VPN. If you can find 100-200K with a VPN at $1 per post, $100-$200K is nothing, as you are paying developers a lot more to do this.
https://www.reddit.com/r/redditsecurity/comments/d6l41l/an_u...
Challenge 1). create a ton of emails
Challenge 2). create a ton of reddit accounts
Challenge 3). generate enough, random activity on accounts to give them enough karma to do anything
Challenge 4). create a system to dispatch and carry out actions with said accounts