Is it required to regularly keep updating droplet?Will it override modified files?

Hello,

Everytime i log in to my digital ocean droplet i get the below message: “209 packages can be updated. 104 updates are security updates.”

I had two questions wrt this: a. Is it required to keep updating the droplet? What are the security updates? Will doing these updates override the settings that i might have changed in the files?(For ex: i have made a few changes in nginx and tomcat files in the server).

b. Now i need to install Postfix for sending emails. I intend to follow the steps mentioned in this link and this. These links required the use of command : “sudo apt-get update”. Are these commands going to update all the existing packages that i have? And will these also override the settings that i might have changed in the files?(For ex: i have made a few changes in nginx and tomcat files in the server).

Thanks in advance, Kavisha.