Some of my best scored shorts are uploaded via web (also in mobile)
Uploading from YouTube app lets you to add sound, texts and filters to a prerecorded video (yes, even a downloaded reel or TikTok video) but you can't use the presetted content for the fields
I like to use the autocrop tool of TikTok to mask downloaded content of third parties. I choose a template, the filter, the music, the texts to add to the video,...
Then I save the finally result to my mobile gallery and I upload the video using the web version of youtube studio on brave
Using it, all the values I have presetted to title, description, tags, language, category,... are charged automatically (in the yt or studio apps this values are not charged)
The only thing I do is going to yt app to change the frame of the video I want to show as cover
I do this, because adding tags in the app is a nightmare (the copy/paste of a list separated by commas don't work on mobile and I have to add one by one, and English is not my native language with the high risk of misspelling that represent that)