Re: http and https on same server

Some reading material;

http://serverfault.com/questions/578648/properly-setting-up-a-default-nginx-server-for-https
http://forum.nginx.org/read.php?2,229949,229949#msg-229949
https://tech.mendix.com/linux/2014/10/29/nginx-certs-sni/

It more or less depends what type of clients connect, SNI support and how you define the first server block.