Yes crxde performance will be impacted if you have more than 1000+ nodes in a single folder. You can find more details here - https://www.netcentric.biz/insights/2019/01/not-break-aem.html 

You can connect it to running AEM instance JVM to monitor the stats of standard JVM provided and AEM specific Mbeans. In your AEM startup script you need to add the following system variable. -Dcom.sun.management.jmxremote.port=portNumIf you require authentication then you can set it via -  -Dcom.su...

The assets from remote assets instance are synchronized when you search for them in the content/assets finder. So I guess in this case you have a path browse field and not using drag and drop feature from assets finder. You can update your dialog to use the image drag and drop field in this case. On...

One possible solution could be to author the banner in a regular page(not experience fragment) and then use reference component to pull in the banner node from the source page. https://helpx.adobe.com/in/experience-manager/6-3/sites/authoring/using/default-components-foundation.html#:~:text=The%20Re...

 You can use AEM Modernization tools for updating the existing page properties. More details can be found here - https://opensource.adobe.com/aem-modernize-tools/pages/configuration/component.html 

You should prefer to store UGC outside of AEM in an external store. If not possible then use Sling content distribution to synchronize user data across publish instances.  Reference -  https://helpx.adobe.com/in/experience-manager/6-3/sites/administering/using/sync.html 

What version of AEM are you on ? It used to be bug in previous Apache sling versions. References- https://issues.apache.org/jira/browse/SLING-4814https://issues.apache.org/jira/browse/SLING-7190 https://issues.apache.org/jira/browse/SLING-3147 

You need to enable the /info property in dispatcher farm file. Reference - https://stackoverflow.com/questions/43461109/examine-cq-dispatcher-from-client 

Have you looked at the AEM Assets reports feature which has a Files report. The Files report shows the list of assets used inside a folder.  https://experienceleague.adobe.com/docs/experience-manager-64/assets/administer/asset-reports.html?lang=en#generate-reports 

Have you checked the error logs of publish instance and replication agent ? Do you see any errors there ?