Zero reason to go for multiple small drives.
Especially on M.2 drives with very limited number of ports for them, it's best to buy the biggest size you can afford easily.
For easier organizing of data on same drive there's good old partitioning.
And it doesn't matter on SSDs, if there are half dozen programs doing random accesses around drive simultaneously.
In fact having dozen+ programs doing that is the only way to reach those advertised IOPS numbers:
Random access read performance with single access at time from single working thread is only little better in NVMes than in SATA SSDs.
And big marketing numbers are only achieved by having many reads going on in parallel and with big pile of them in queue for controller to be able to choose from for optimal pattern of accessing actual NAND cell locations.
(kinda like NCQ in HDDs)
