Your comments

For plain text notes, EssentialPIM works fine. Desktop version permits rich text formatting, but not android version. At least you CAN enter a Note on android & sync it to the desktop, across your own lan.

The other components of EPIM work fairly well, and it will sync with your Google accounts IF YOU WANT IT TO.

For "Secure" notes, eWallet offers robust cross-platform sync. Have used it for years, although primarily as a form based database as, again, its "Notes" capability is strictly plain text. (Still a wonderful app for things like passwords, account info, serial numbers, license numbers, warranty info - a wide range of discrete data, as opposed to free-form text.)

The best Windows Desktop free-form database application I have found is RightNote (Pro) - but it lacks an android version. It will sync with Evernote, for users of that product - but, again, you are now in the cloud.

Perhaps more useful, it has the ability to EXPORT a database as a "Webbook." This is fine for "static" data which you simply wish to have portable access to, but does nothing for data input while in the field.

Really, really, really MISS the old PhatNotes Windows / Windows Mobile pair.

Then again, with many (most?) ANDROID apps, also Miss SPELL CHECK...

Another vote for an Android version. 
For best usability, the ability to add data to either version (mobile / desktop) AND then to sync between the two would be desired.