You can put the /home as big as you want it. If you have lots of music, pictures, documents, etc, you could make it 1TB if you felt like it. No limit on how big or small.
Perfect! Since I am a musician,I have tons of music,albums,.mp3's,music videos,and related documents all pertaining to my business.
As for how a separate partition works its actually more like having a secondary drive in windows than a file directory.
Its like if you had two drives in windows, one for the OS and the other you store your files onto (very common on SSD desktop setups due to limited space on SSD's)
That's great! Since i just installed my two OS's- Win10/Ubuntu Studio on my Samsung 512 SSD,I have a 600 Gig drive that is empty.I will use it for my /home partition. That should be plenty of space to hold .wav recording files,projects,etc. as well as all my music! I also have another 160 gig drive which I havent decided on it's use yet. Probably for backups.!!!