Do you want to use it for doors like school/work/apartment complex? Or more for your own door locks? The community has put together a great document that lists a bunch of different RFID door locks and their compatible chips here;
As for password storage, you may be interested in the upcoming VivoKey Apex which is due out some time this year and will have the ability to run javacard applets and a password vault is one of the apps in development right now. You can keep an eye out on the Apex progress in this thread;
For other kinds of access like apartment and workplace doors, it all depends on what kind of protocol they use. A great starting place is the NExT which is a single implant with 2 RFID chips - a low frequency which is pretty common for a lot of access systems, and a high frequency which you can write to and scan with your phone, which people use for all sorts of things from sharing contact details, social media/web links etc.
This forum is a huge repository of information, albeit a little overwhelming at times. But take some time reading lots of posts to get a better overall picture of how things work. It’s hard to answer such a broad question as “which implant should I get?” as it’s pretty use-case based.
Have a look through the WIKI and FAQ sections too!
But feel free to ask questions, people are always willing to help you out but try to do a bit of research first so it’s easier for us to help you out with the specifics 