Oh i've been down this road before, and i ended up with a new Synology, though i keep my lab part on a separate machine and use the Synology for storage only :)
Benchmarks are nice, but you're comparing an old NAS to a brand new one with significantly more computer power, and had you compared to a new Synology, you'd probably arrive at the same findings.
Parts of you power consumption could very likely be from your choice of hard drives. The 8TB Seagate Ironwolf has an average power consumption of 8.8W [1], where a WD Red 4TB requires at most 4.8W [2]. With 4 drives, that's an additional 16W of power consumption right there.
Another thing you could try is to enable powerd and measure if it has any effect on the power consumption. In case it does, you can enable it in TrueNAS Core by adding it as a tunable via the web UI. System -> Tunables -> Add Type = rc.conf Variable = powerd_enable Value = yes
Benchmarks are nice, but you're comparing an old NAS to a brand new one with significantly more computer power, and had you compared to a new Synology, you'd probably arrive at the same findings.
Parts of you power consumption could very likely be from your choice of hard drives. The 8TB Seagate Ironwolf has an average power consumption of 8.8W [1], where a WD Red 4TB requires at most 4.8W [2]. With 4 drives, that's an additional 16W of power consumption right there.
Another thing you could try is to enable powerd and measure if it has any effect on the power consumption. In case it does, you can enable it in TrueNAS Core by adding it as a tunable via the web UI. System -> Tunables -> Add Type = rc.conf Variable = powerd_enable Value = yes
FreeBSD Wiki also has some Tuning Parameters [3]
[1]: https://www.seagate.com/www-content/datasheets/pdfs/ironwolf...
[2]: https://documents.westerndigital.com/content/dam/doc-library...
[3]: https://wiki.freebsd.org/TuningPowerConsumption