Price seems decent for lifetime which is 20$. Also it's processing on server side rather than client machine so user can do it from mobile, old laptop and don't need to use any other software.

for that flat price, i bet they are already working on ffmpeg via webassembly. otherwise they will go under or dishonor those early clients pretty fast.

What is an easy way to do this manually? I can’t think of any, but then again u don’t use TikTok etc

Aren't you just cutting the screen and playing a subway/gta/etc video below?

It can be done in any editor in a few clicks

Auto captioning will surely help, you can also provide styles for captions.

I remember revid.ai does similar stuff you can take inspiration from.

Download CapCut for free, drag both videos into your media panel, now click + on them both to drop them on the timeline. Make sure the ratio (under the preview window) is set to 9:16. Click on each video and move it around until you have it lined up where you want it. Export.

i was impressed with the features which kdenlive provides; had a small learning curve for some of the basics but went in expecting that