I see two aspects.
The first is that a traditional SSD contains RAM for caching and their whole construction is not powerloss save. So any crash or power outage during a write (or internal garbage collection) can result in a dataloss even on confirmed writes, not what you want when you enable sync write. I would say either you accept a possible dataloss on a crash but have full performance with sync disabled or you care about powerloss protection on an Slog. A desktop SSD can only give a small performance boost on sync writes with only a small advantage for your data security on a crash.
On a traditional flash performance lowers with usage so you need trim and garbage collection. A concurrent workload between L2Arc and Slog can heavily affect slog performance. This makes using Flash SSD partitions for both a bad idea.
With Optane this is different. As Optane can address a cell directly for read/write with an extreme low latency there is only a minimal degration on writes or concurrent workloads. I see no performance problem when using a partition for L2Arc and Slog.
Remains the powerloss protection aspect. While a 900P has no ram for caching what limits the risk, Intel does not guarantee powerloss protection (they did when the 900P came up but removed this specification later. Only the 48oox has guaranteed powerloss protection). Over all I would accept a very small rest risk for most use cases when use it as an Slog. Only when you must ensure a highest datasecurity for sync writes you must use the expensive 4800X series.
