[DOCS] Clarify xpack.security.enabled info (elastic/x-pack-elasticsearch#2166)

Original commit: elastic/x-pack-elasticsearch@140e330973

docs/en/settings/ml-settings.asciidoc

@@ -12,8 +12,11 @@ Set to `true` (default) to enable {ml}. +
 +
 If set to `false` in `elasticsearch.yml`, the {ml} APIs are disabled.
 You also cannot open jobs, start {dfeeds}, or receive transport (internal)
-communication requests related to {ml} APIs. The {ml} icon is also not visible
+communication requests related to {ml} APIs. It also affects all {kib} instances
-in all {kib} instances that connect to this {es} instance. +
+that connect to this {es} instance; you do not need to disable {ml} in those
+`kibana.yml` files. For more information about disabling {ml} in specific {kib}
+instances, see
+{kibana-ref}/ml-settings-kb.html[{kib} Machine Learning Settings].
 +
 IMPORTANT: If you want to use {ml} features in your cluster, you must have
 `xpack.ml.enabled` set to `true` on all master-eligible nodes. This is the

docs/en/settings/security-settings.asciidoc

@@ -13,8 +13,13 @@ and  <<ssl-tls-settings, encrypt communications with SSL>>.
 [[general-security-settings]]
 ==== General Security Settings
 `xpack.security.enabled`::
-Set to `false` to disable {security}.
+Set to `true` (default) to enable {security}. +
-Configure in both `elasticsearch.yml` and `kibana.yml`.
++
+If set to `false` in `elasticsearch.yml`, {security} is disabled. It also
+affects all {kib} instances that connect to this {es} instance; you do not
+need to disable {security} in those `kibana.yml` files. For more information
+about disabling {security} in specific {kib} instances, see
+{kibana-ref}/security-settings-kb.html[{kib} Security Settings].
 
 [float]
 [[password-security-settings]]