There’s also the possibility they’re referring to the current draw through the mobo connector itself frying things. A couple of HDDs at 12V, 10W will be pulling almost 2A which can be a lot for some circuit board traces, but there’s no great way know what the board can handle without documentation from the manufacturer or someone with relevantt engineering experience well above what a typical computer repair shop would have.

If I were OP I would just roll the dice and try it out. Its not as if old Dell office PCs are high dollar items.

Those are the molex to sata power adapters that are a fire hazard. I haven’t ever heard of this type causing issues and have been using them for years and years without issue.

This is what i have. Amcrest cameras tied to an Amcrest NVR which offers remote viewing, recording, and playback and then also tied into Frigate and Home Assistant also for remote viewing, event notifications, etc. I could ditch the NVR but I’d need to get a POE switch and I like having it as a backup.