Just a heads up, you can create drives up to 256tb, you just have to type it in. You can also resize drives, but you need to ensure the cluster size you set on creation will support the larger drive sizes. I created on massive 256tb. I'm not saying this is the best setup, but from a performance perspective it works just as well as my 2tb test drive in terms of speed. Cloud drive doesn't actually allocate the full drive space on creation, so I aside from the OS needing to mount the file allocation space, I don't think you will see performance differences based on drive sizes.
It's also important to note that although some settings can be changed on the fly or when mounting the drive, some settings cannot be changed once the drive is created unless you destroy it and start over. Off the top of my head the ones that cannot be changed I believe are: chunk size, cluster size, whether or not the drive is encrypted, if encrypted the key itself, and I think a chunk verification setting, but I could be wrong on that last one.
Min download size and chunk cache size can be changed, but not on the fly. You need to dismount and remount the drive to change this setting.
Prefetch, up/down thread count, bandwidth throttling and cache size/type can all be changed on the fly.
The biggest perfomance gains I've seen are from the chunk size, min chunk download/upload, read/write i/o threads and prefetch settings. These settings vary drastically depending on what type of media you are storing. If it's small data files, then smaller chunks are better. If it's large multimedia, larger chunks are better. I'm doing primarily multimedia storage so my settings are:
5/5 read/write threads
20MB chunks (max for Google Drive)
100MB Chunk Cache
20MB Min Download size
50GB Cache, Epandable (I've changed this from 20 all the way up to 80GB without much difference in streaming performance, however because I frequently move large files around, I benefit from the increased cache.
120 Second Window
250MB/250MB Up/Down Throttle
You'll probably notice that most others doing multimedia have much more aggressive prefetch settings than mine. In my case, these settings allow 3 to 4 HD streams without issue, and more aggressive prefetch settings cause me throttling and disconnect issues.