The functionality you are looking for(scaling) will be something you will need to setup with your host. May be you need some load balancer.
The slowness of upload is beyond control of the plugin as it depends on your number of users server resources, file sizes etc.
My suggestion will be to look for offloading the media(if there is any media plugin that directly uploads to cloud instead of your server) or get in touch with your server support and get the load balancer setup for scaling your installation.
You must be logged in to reply to this topic.