Whats the out speed of a Node Balancer?

The out speed of a Node Balancer is only Limited by the Backend Linodes. Essentially what happens is someone goes to your domain that points to the IP address of the Node Balancer. It then passes the request on to the backend Linode and the Linode takes over from there. You are only limited by the out speed of your Linodes. So if you have 2 Nanodes behind a Node Balancer your total out speed is 2,000 Mbps (2 x 1,000).

Do keep in mind that connection rate can limit performance as well.

It's one thing to balance relatively few http requests that process large amounts of data each - and it's quite another to balance a lot of small http requests from distinct clients.

So there are two potential limiting factors here - 1. some overhead for each new connection (esp. for https) 2. raw throughput once a connection is established.

I'd recommend benchmarking a Node Balancer vs. let's say a $20 Linode running nginx as a load balancer / reverse proxy - and then deciding.