To know how ConnectALL handles the Log4j 2 vulnerability issue, please read the article here.

Does ConnectALL impact any real performance issue on server

ConnectALL has a very minimal impact on your application server especially when you poll for changes quite often such as every minute or every 5 minutes. The one thing that can impact server load is if you have a lot of very large attachments (>100MB) to sync. You can avoid this by not syncing attachments, or syncing the attachment url instead of the entire file.