One thing to keep in mind is Samsung tends to alter their phones in a lot of different ways, a lot of them very subtle. Also, the Android OS itself is continuously evolving so while there's generally consistency in fundamentals between versions, there's typically a lot of other changes. Some in the background that you'll rarely if ever interact with, some are interface changes that you will. So when looking around for information, it's pretty important you do searches centered only on a) a Samsung S7 and b) whichever version of Android you're currently running. It's not a matter of instructions or tutorials being able to apply to all Android phones, there's just too much variance involved.
That said, there's also the issue of setting up a phone. Most of us use our phones in different ways. There will of course be some commonalities but it's a rarity to have two different people having their phones set up the same way. My suggestion is for you to just sit down, open up the Settings app, and start going through each option one at a time (note that several have their own sub-menus and some of those have their own sub-menus). This way you'll learn about the features specifically on your phone, not some generic walk-through vid that may or may not apply to your S7. Set things up in a way that will suit your purposes, not someone else.
As for things like which email app or which browser app to use, those are also very subjective points. Personally I've found the default Samsung apps to be fine for general usage but lacking when it comes to more advanced needs. But a lot of this determined by what you feel most comfortable using. Use the default Samsung email app for a bit, then install the Yahoo email app and try it out to see which of the two you prefer. The Yahoo app will probably have smoother integration with your Yahoo account but that's going to be more behind the scenes, The big difference up front are the different user interfaces, pick the app you feel most comfortable using. (If the Yahoo email app, then just disable the Samsung email app. If the Samsung email app, uninstall the Yahoo email app.) Regarding having apps you don't use on your phone being a problem for you. Try not to fixate on this point. You can disable but not remove some of those Samsung-install apps, and keep in mind when disabled, an app isn't running in the background or doing any online activity. Also, there are apps available that allow you to remove 'system-installed' apps, and they don't require you to root your phone. (... but do so judiciously as you don't want to remove anything vital to the operating system itself).
As for that business email account, you'll need to manually enter the proper configuration settings into whichever email app you use. You need to contact an IT staffer at work who manages the email accounts or whomever maintains the email server itself to get the settings info. It's not a burdensome task to manually set up an email account in an email app (the info most likely just being your account name & password, the incoming and outgoing server names, and a handful of corresponding numbers), but the settings do need to be exact.
