Because @Locklear93 and @zenzen have answered well, I only want to say that I personally prefer the Erase Disk Option when installing Zorin only because You don't have to set up anything manually.
And You don't have to handle if a seperate Partion have reached limited Space. Because all is under one Roof it takes simply the Space what is needed.
First, if you have plenty of RAM (16 Gb or more) you should not need to have a swap partition.
First thing to create on a clean drive is:
300 Gb formatted as FAT32 and labelled /boot/efi
Create a 'root' partition formatted as Ext4 FS and make it 80 Gb in size, then label it '/'.
Format the remaining space with Ext4 FS and label it as '/home'.
I would suggest you use GPT method of partition creation over 'mbr'.
In terms of your growing music collection you might want to convert to .flac to save on space, as the app Audacious can play these.
Just a word of caution before proceeding. I hope you didn't enable copyright protection in Windows Media Player as this locks all your music to Windows Media Player. I discovered this back in XP days.
The problem with auto install is that you have everything in one place on one large partition. If something goes wrong you could lose data, and in any event it is worth getting an external drive to back up to regularly. If you intend to use 'Timeshift' to take snapshots of your system, be sure to format your external device to Ext4 FS as if you save to the preformatted drive, (they are normally formatted to NTFS) you won't be able to access your snapshots for system recovery.
@zenzen: in one of your answers above, you quoted another post that mentions "backing up individual configuration files, bookmarks and similar application specific files". I currently use Brave browser, & have figured out how to transfer bookmarks - just curious if I need to worry about transferring any of the other files mentioned?
That will depend on how many programs you have installed, and whether you care about keeping any relevant configuration and/or data files about those. For example, you might be also interested in backing up Firefox's bookmarks if you're using it in addition to Brave.
It's just like moving to another house in real life: there's always something missing or some box that has been "misplaced" 
Just make sure you have a good inventory of what you want to keep around and make copies of it. When you're done installing the new OS, copy them back.
Thank you @zenzen... good analogy 
. Brave is my only browser. But as far as keeping any config files & application specific files for other programs, or how to do so, I haven't the faintest clue. How would one know what's important and what's not? Can you give any examples of other types of programs I might want to do that for? Will it be a huge headache just reconfiguring programs/apps after installation? 
Only experience can tell you that, I'm afraid, since your use case will be different than mine and others.
To give you an example, I use multiple browsers at once for different purposes. Each browser has its own bookmarks, extensions, site settings and other configurations. Having to set it up every time I re-install the OS is a bit of a pain because it takes time.
So, I simply copy the profile folders and drop them in the new OS, and it's as if nothing ever happened. Well, currently I have my drive partitioned with a dedicated /home partition, so I don't need to do this anymore. But you get the idea.
Another example might be custom fonts that you may have downloaded, or things like the bookmarks from the file manager:
In short, anything that has a "Export to..." option in the menu bar and that you think might be worth keeping around.
But don't over think this too much. All of this can always be re-configured as needed, it's just a convenience. Perhaps the most important thing to back up are actually the bookmarks because those are tough to remember, especially when you have dozens or hundreds...