GPT is the newer standard, supports higher capacities/partitions, and is fully compatible with UEFI.
MBR is older, limits your capacities/partitions & requires legacy (BIOS) to be enabled.
GBT, on paper is a little faster..... in practice, they're very much the same in boot/response times, assuming all else is equal.
GPT would be my suggestion.
Cluster size relates to throughput, for files <64K (likely the bulk of your OS and common files/folders), you'd see wasted space of XKB (where XKB = 64K - file/folder size) utilizing 64K. For Audio/Video files, editing etc - the throughput is beneficial as you'll require less reads to get the same data. That would only relate to a dedicated drive for that media though (potentially a partition, but not sure if you can specify on a per-partition basis).