Hi
You do not have to change the Wi-Fi name or password , that is personal preference if you do. I change mine so it's easy to remember when setting up devices, but you don't have to.
Again, with the router login, it's best to keep this as admin, the password itself is on the back of the router under the Wi-Fi card, and is unique to the router, so unless someone has physical access to the router, there is no need to change it, but if you do, and you forget it, you will have to factory reset the router to gain access. so write it down and keep it safe.
If you set up a guest Wi-Fi for friends / family when they visit, you can find useful resources on the web such as qifi.org that can generate a QR code they can scan with their devices to give then Wi-Fi access.
Thanks
Karl.
