About database reliability and constraints

question 1
If a file imported to the database is exported as a “files and folders”, is the exported file the same as the original file?

Question 2
If the file imported to the database is edited with an external application, will the edited content be accurately reflected in the file in the database?

Question 3
Are there any restrictions on the type, number, or size of files that can be imported into the database? For example, if you import hundreds of video files, will the app slow down?

Im/exporting does not modify files.

Sure. The file in the database is actually edited, not a temporary copy.

Up to 300.000 items and 300 million words are recommended per database, see File > Database Properties.