Not a Plex user (I use rclone for archiving my backups, not streaming in any way), but I'm generaly satisfied with a VPS-M from these guys: https://contabo.com/?show=vps
I get ~10MB/s sustained with rclone to my encrypted GDrive remote, both on reading and writing, and very decent CPU, RAM and local disk space. And of course their service is KVM-based, as I would never store any sensitive information (like my encrypted GDrive credentials!) on an insecure setup like you get with container-based (OpenVZ, Virtuozzo, Docker, etc) containers. Minimum security is a machine where you have direct access to your own hard disk (specially a virtual one) so you can partition and encrypt it with LUKS to store that sensitive information).