Mostly yes because server chassis are very compact and sometimes use proprietary connectors and fans. Still, many people have done that with good results, have a look in YouTube to know which server models are best suited for that kind of customization.

I've not been successful trying this with HPE servers. Most server fans (Foxconn/Delta) run 2.8 amp or higher. Not aware of any "silent" gaming grade fans that use more than 0.38 amps. That's not even considering the CFM.

Why would current be relevant here? Shouldn’t operating voltage be the only thing that matters?

Amps * Volts is power. Power is a proxy (a moderately good one) for air movement (a mix of volume/mass at a specific [back-]pressure).

It’s not likely that a silent 2W fan will move a similar amount of air as the stock 14W fans. The enterprise gear from HPE is pretty well engineered; I’m skeptical that they over-designed the fans by a 7x factor.

Operating voltage tells you “this fan won’t burn up when you plug it in”. It doesn’t tell you “will keep the components cool”.