It’s my understanding that they will send it to a certain number of followers, test for engagement. After xx views, it will be held for review. Sent to a large group, test for engagement. and so on with another two or three reviews to ensure content is appropriate for promotion.
Tik Tok is very good for getting started and is much easier to grow quickly. If your content is consistently good you can gain a few million followers within a few months. I think your first few videos are critical as they determine hidden tags placed on your account and how much traffic future content will get.
As with any social media platform, they care about engagement. Keeping people watching for as long as possible. Tik Tok seems to prioritise new creators and not many can last long term on the platform.