To DIY you can buy your own domain and attach it to any paid email provider, then you get an infinite amount of temporary addresses. e.g. if you own @ rumschlumpel.blahblahblah.org then you can create abc@ , xyz@ , abc123@ , etc. as much as you like.
Just about all the email provider suggestions in this thread have a paid tier that you can configure your own domain with.
On a headless seedbox Deluge/ruTorrent/Transmission are still reliable, most of the paid seedbox services still default with those.
qBittorrent is hugely popular on the desktop front and has been getting more popular as a headless client now that the web ui has improved, also look into qbittorrent-nox if you don't have a gui to do initial setup with.