I have found KeePassium to be probably the best password manager for iOS that uses the KeePass database technology. Specifically, I have compared it with KeePass Touch and Strongbox, finding that KeePassium is the most accessible and supports most features for free among those. In my opinion, it also beats BitWarden and 1Password either in terms of accessibility, usability, feture richness or price, though these use different technology for data syncchronization and storage than KeePass, more on that below. .
Passwords synchronization with other devices
As opposed to BitWarden or 1Password which take care of synchronization themselves, if you want to syncronize your saved passwords or other database entries in KeePassium, you have to create and place the database file to an online storage like iCloud Drive, OneDrive or Dropbox yourselvf, and access the same file from other KeePass based application, the most accessible and feature rich one on Windows is called simply KeePass which is available for free. On macOS, I have found the most accessible to be Strongbox, MacPass and KeePassium, all of which are also for free.
KeePassium for macOS
KeePassium is available as a universal app which runs also on macOS, where the user interface is almost identical to the iOS version, but in the macOS version of KeePass, it is unfortunately not yet possible to work with file attachments using VoiceOver, and there are some other quite serious accessibility bugs, like not being able to open database with VO + spacebar but only with Left mouse button click simulation. If you are looking for a more accessible and feature rich password manager for macOS, then I would recommend Strongbox.
Comparison with paid version of KeePassium
The limitations of the free version of KeePassium is that it supports work with only one database, plus is missing some other convenience and security features the complete list of which can be found here. But these look rather marginal to me. The paid features come either with KeePassium Premium as an in-app subscription based purchase for $2.99 per month or $14.99 per year, or with KeePassium pro as a one-time lifetime purchase for $59.99.
Other opinions or questions?
How do you like KeePassium, do you have some questions or suggestions for even greater password manager?