When I spin my pedals by hand they spin very fast and long, almost like a fidget spinner, making a sound too. I somewhere read that this means that the bearings are 'dry', and that pedal spin should be more 'buttery', like they shouldn't spin very long, and have more of a dampened, silence feel to it. Is that correct and do I need any special grease? I got a tube of "Grease with Teflon" from Decathlons BTWIN brand. Would that work?
From your description yes, your pedals sounds to be not greased properly. If you please could post a photo from different angles, it would be easier to provide further advice.
In general, if there is a possibility of disassembling, you should do this and repack the bearings, the same way as you would do with cone hub.
For temporary solution or if the pedals cannot be disassembled in non-destructive way, a thin grease or even chain lube may be suitable, but then the pedals should be greased as often as you lube your chain.