A few days ago somebody here posted that they needed to rebuild their server. They were using 100% of the space on / instead of using a /home/ partition. That got me wondering why having a separate partition for your data isn’t promoted more, are there any disadvantages to this? I’m thinking about things like permissions problems after changing the system, getting the drive to mount properly at boot, quickbox seeing the drive correctly etc
Have any of you experience using this setup?
There is really no difference between the two. Your data is still stored in the very same locations regardless. The issue is when people mount a /home partition and leave little to no space on /. Things such as a Plex Library with a lot of data can easily exceed 10 or even 20GB given enough media and time.
When installing just one / partition, this issue does not exists due to plenty of space allowed to drive… all of it in fact.
QuickBox has no issues rendering the data from either a / or a /home partition. The issue arises when people use pointless mounts such as /data on an install. There really is nothing wrong with that, as that is a matter of labeling and preference I suppose, however; QuickBox is aimed at a typical market rather than a global market… typical being the standard mounts you would find with the majority of providers on the market.
Space is a good shout. By default online.net gave my /boot partition 100mb of space. Caused all kinds of hell when the kernel needed updated.
I suppose there is nothing to stop you giving the system 120gb if storage, I highly doubt Plex meta data would get that big. I’ll keep this in mind the next time I’m building a box. 
An example would be that of @dtech_banned’s setup. He has about 2,000 (5000) movies and something like 300 total Shows (seasons etc) I think he said his Plex Library was at 40GB? So, it should never reach 120GB… unless… you’re insane and watch the worst movies imaginable and collect them all due to some psychotic hoarding disease. 