To follow this up - how can you test multiple sites with the setup? using the IP in server name directive does not seem to work with easyengine. Dunno why - but simply doesn't.
Is the only solution in that case to have only one site active? (by remving sites-enabled symlink?). Usually just switching around the IP in server name from config to config file should work - however it doesn't. There must be somewhere a hidden file configuring this.
It seems to always direct to the first site ever enabled with easyengine, instead of to the site having the IP in the server name or drop back to the default nginx static website in var/www/html/.
Instead I get:
nginx: [warn] conflicting server name "18.104.22.168" on 0.0.0.0:443, ignored
on sudo service nginx -t
Which is crazy for my understanding - because that's the standard way of specifying which website should respond when you go in via IP instead of domain name.
-- so the only way is to setup a new domain for each website you want to test out. Still - the only thing you can test that way is if the page loads - on wordpress i.e. because of forwarding rules it's basically impossible to get to wp-admin or login.
So you basically have to setup another test site - again with another domain and play in your real website and change everything to see if it goes through smoothly - note down any problems - try to solve them back on your old server - and then finally tell your provider to switch the servers (so your new server gets the old I.P. and the old server the new I.P.).
What I would do beforehand though - is change IPV6 to new server - very few people use it right now - so you can have a quick go at it live. ( I have about 10% IPV6 users - so it's worth trying that out at night - and then if it works you can safely either change the DNS over - or let the provider switch the server rack - which if possible is always better because you don't have to go into maintenance mode that way. ). If you're even more tech savy you could run your wordpress database from a third server - for the switching time (or in general) - I'm not tech savy enough to do that (or don't want to spend the time learning it).