I've stopped auto defrag on Win 10 but run it manually once in a while. Stopped using third party defraggers a long time ago as they hammer the HDD, in my opinion, and as you say - show no better performance.
As for modern SSDs I'm not sure that 'trimming' is necessary either.
Trimming does help SSDs if you have a lot of small files that get updated regularly. If many small files fall in the same block then that block will remain in memory and not actually be written until a different block needs that memory.
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