For best performance over the Internet, a VDSL2 or Fibre connection or equivalent is strongly recommended (cellular or satellite connections will be higher latency). And the server should be located geographically close to the clients that will connect to it (locating your servr in another country will not provide responsive performance).
Be sure to turn on the *Run on Server if possible* option in the Report Prefs of your custom reports. Note that reports that operate on a selection of records need to take measures to pass the selection to the server. All standard reports do this.
If your server is accessible over the public internet, we recommend that you enable encryption (SSL/TLS). This requires an SSL certificate, obtained from a certificate authority. You can use the same SSL certificate for native and REST service.