I have not been working with Glide for some time now due to other professional priorities and was surprised to see that the default DB now is Glide Big Table, but it seems that Glide Table is still used for the Users Table.
Ist that correct? If yes, does that mean that there are actually 2 DBs at work?
I remember that one had to be careful with Glide Tables in terms of Security, using Row Owners etc. is that still necessary with Glide Big Tables, e.g. when a query is used to filter the data of a single user?
Yes ! Row owners are still the only security feature to hide data with restricted access.
Filters and visibility conditions are not security feature. You will be able to filter for easy filtering of data, but they are still downloadable if not restricted by row owners.