I have a few that I put in a folder within obsidian.
But the majority i have as links to files on my one drive, as i am not sure if the Obsidian folder grows, I wont have the storage capacity on my Ipad or Phone to be able to sync.
I have a few vaults with relatively large attachments. One I don’t sync (my work vault), and the others I sync via Dropbox (my creative vaults). If the Dropbox vault got too large for my mobile devices I could use Dropbox to selectively sync only the files I wanted.
I sync a couple vaults using Obsidian Sync for the convenience, but neither of them have large attachments.