I personally have an external hard drive for this. I don't trust any online host at all, because either your stuff could get removed for "DMCA"/similar or your internet is slow and you cant quickly access your stuff. (Or the server has problems and you can't access it either)
2TB HDD, format in exFAT, using Veracrypt for encrypting specific parts into containers. Have another one as a backup if you really value your stuff.
For pictures I remove metadata with mat2 and optimize them with jpegoptim / pngquant. This alltogether saves multiple GBs of storage space.
For videos i either optimize them with constant-rate-factor 25 or i even downscale them to default 1280x720 30FPS. (I dont need 4k 60fps, not even for any kind of movies / streaming). This saves the most storage but takes the most time.
Folder structure is either per category or per media type.
Example: I have media/cosplay/name_here for videos AND images of name_here, but i keep rather unsorted videos in media/videos/random.
If you run out of storage space really ask yourself "Do i really need this? Will i ever look at this again?". I once had 6TB of random stuff collected over the last few years, but I only kept what I really want and now am back to one HDD (+one backup HDD ofcourse, no backup no pity)
