Here are my configs:
Took me about 2 weeks to make them work.

[code]#AUTOMATICALLY GENERATED - DO NO EDIT!

fastcgi_hide_header X-Powered-By;
fastcgi_cache_path /srv/cache levels=1:2 keys_zone=MYAPP:500m inactive=60m;
fastcgi_cache_key "$scheme$request_method$host$request_uri";
client_max_body_size 128m;

server {
    listen 80;
    server_name example.com www.example.com;
    return 301 https://example.com$request_uri;
}
server {
    listen *:443 ssl http2;
    ssl_certificate /etc/letsencrypt/live/example.com/fullchain.pem;
    ssl_certificate_key /etc/letsencrypt/live/example.com/privkey.pem;
    server_name example.com;
    access_log /var/log/nginx/example.access.log;
    error_log /var/log/nginx/example.error.log;
    root /srv/example.com;
    index index.html index.htm index.php;

 include /srv/conf/example.conf; #modx part goes here

location ~ [^/]\.php(/|$) {
     add_header Strict-Transport-Security max-age=15768000;
     fastcgi_cache MYAPP;
     fastcgi_cache_valid 200 60m;
     add_header X-Cache $upstream_cache_status;
     set $no_cache 0;
     if ($request_uri ~* "/(manager/)")
    {
    set $no_cache 1;
    }
     fastcgi_cache_bypass $no_cache;
     fastcgi_no_cache $no_cache;
    # serve static files directly
    location ~* ^.+\.(jpg|jpeg|gif|css|png|js|ico)$ {
        root /srv/example.com;
        access_log        off;
        expires           30d;
        break;
    }

fastcgi_index index.php;
include fcgi.conf;
fastcgi_pass unix:/var/run/ajenti-v-php-fcgi-examplecom-php-fcgi-0.sock;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;

    }

}[/code]

[quote]include /srv/conf/example.conf;[/quote] is a modx config
[code]charset utf-8;
autoindex off;
include /srv/conf/basic.conf;
include /srv/conf/additional.conf;

access_log off;
log_not_found off;
error_log /var/log/nginx/nginx-error.log warn;
location = /favicon.ico { access_log off; log_not_found off; }
location = /robots.txt  { access_log off; log_not_found off; }

#MODX IMPORTANT
location /manager {
}
location /assets {
}
location / {
    #try to get file directly, try it as a directory or fall back to modx
    try_files $uri $uri/ @modx;
}
location @modx {
    #including ? in second rewrite argument causes nginx to drop GET params, so append them again
    rewrite ^/(.*)$ /index.php?q=$1&$args;
}[/code]

[quote]include /srv/conf/basic.conf;[/quote]
Its [url=https://github.com/h5bp/server-configs-nginx]h5bp/server-configs-nginx[/url]. They are handy for SSL and other optimisations. Play them if you need.

[quote]include /srv/conf/additional.conf;[/quote]
Gzip optimisation
[code]#keepalive_timeout 20s;
sendfile        on;
tcp_nopush      on;
gzip on;
gzip_comp_level    5;
gzip_min_length    256;
gzip_proxied       any;
gzip_vary          on;
gzip_types
    application/atom+xml
    application/javascript
    application/json
    application/ld+json
    application/manifest+json
    application/rss+xml
    application/vnd.geo+json
    application/vnd.ms-fontobject
    application/x-font-ttf
    application/x-web-app-manifest+json
    application/xhtml+xml
    application/xml
    font/opentype
    image/bmp
    image/svg+xml
    image/x-icon
    text/cache-manifest
    text/css
    text/plain
    text/vcard
    text/vnd.rim.location.xloc
    text/vtt
    text/x-component
    text/x-cross-domain-policy;

[/code]