A focused first version usually includes accounts, a vertical feed, upload and processing, playback, likes, comments, sharing, follows, notifications and a moderation queue. Creator tools, duets, effects, direct messages and recommendation models can come later. Each one adds a new failure surface, so I would rather ship a clean viewing loop than a long feature list that no one can operate.
I can work with your existing video backend or help choose between a managed service and a custom pipeline. The trade-off is usually cost and control: managed transcoding and delivery get you live faster; a custom pipeline gives you more control over storage, encoding and analytics.