Thank you for your feedback!
1) The .encfs6.xml configuration file should already be hidden and not being displayed. Other dot-files are not hidden automatically because they are only hidden by default in Unix systems, but not e.g. on Windows. We might add an option to hide dot-files in the future.
2) We're using the built-in document previewer in iOS. If this does not display your excel sheets correctly, we recommend to use a third party app like DocsToGo via "Open in..."