if i install mysql and httpd there can be problems with OVM web
If you install httpd as apache web server yes there are issues as is more likely that nginx will lose the battle starting as a daemon/service. Then you will come here complaining you don't have a webui for OMV. You can use apache but configure it accordingly not to share the same port with nginx if you know what you're doing.
There are no issues using mysql, i recommend instead of installing apache use nginx in conjunction with the nginx plugin to launch websites. You can also configure the php-fpm pools with the plugin.