For links, I use Pocket (you can use Wallabag, but I find the interface not efficient at all). For files, you can sync a folder with syncthing (but you only switch it on when you want a quick sync, otherwise keep it off for battery). If you just want to put some file on your phone, install FTP server (free) from F-droid and switch it on when you need it (there’s even an optional switch on quick actions). Use Filezilla or any file browser (if on Linux) to exchange your files. Remember to switch the server off once finished, because FTP is not a secure protocol.

Nextcloud was too slow and bloated for me. I used Seafile for years and it was fine, but at some point I went to some more simple setup : sftpgo to share folders (sftp, dav) and syncthing for the folders I want to sync between devices. You can also set ignore lists in syncthing to ignore large dirs. Keep it simple stupid 😅

No offense, but I suggest you talk to a psychologist about this 🙂 I and many other friends did over here, and it really helps to unlock your full potential (everyone has different problems).

Why won’t you be able to create two accounts?