Speaker stand spikes or something else?

BDR Cones. Carpet doesn't matter. Even better is Cones combined with Round Things.
https://systems.audiogon.com/systems/8367

I’m a firm believer in rigidity when it comes to speakers. You don’t want the speakers to move. You want all their energy from the drivers to create an accurate wavefront. Any movement of the speaker will smear and distort the sound. By the same token you don’t want the speakers to vibrate the floor. If I didn’t have concrete floors, I’d have to put a paving slab on the carpet. Then spike or cone them to that.

Measure your speaker stand base threaded holes or the cones points and make a square or rectangle template. Then get the appropriate length sheet rock screws. Determine the exact speaker placement for each speaker and install the screws, into the floor, thru the carpet to a height that is good for your cones or spikes. Then place the stands with spikes installed into the X of the Phillips screw heads. The holes created by the screws will never be detected in the carpet. Just make sure when all is installed, the stands are just above the carpet and are level. This is a bit tedious, but works well.