Spokes should not twist (beyond 1/4 turn) while building or repairing. Keeping aero spokes straight requires a holder and a host are available from the likes of DT, Sapim, Park, etc.
One very nice holder has been needlessly absent from the broader market, the Cyclus Geganhalter für AERO-Speichen. This device offers 6 sizes. Hard plastic is long wearing and harmless to spoke surfaces.
The 6 sizes vary from just below 2mm to about 0.8mm. Tool body is 25mm thick and total diameter is 75mm.
There is no "best" spoke holder. It's all about ergonomics and your own build style. Right or left handed? Turn from above or below the nipple? What spoke wrench? Behooves you to own most logical aero holders so you have choices and can focus on those that work best for your building.