Bass traps - foam cushiony items from Amazon ok?

It is highly unlikely that any foam thing for $25 will be an effective bass trap. You might find this interesting, an impartial video by a professional:

https://www.youtube.com/watch?v=Jdi6jKLhfbw

Just walk around your room and clap your hands sharply. If you can hear the echo, you need a foam panel on ONE of the walls.

Yes, that's reasonable, but it's NOT bass trapping -- it's treatment for slap echo, which is much higher frequencies.

Artnovion and Vicoustic have the most beautiful products to my eye. But they are not cheap. The best value often is provided by GIK, who will provide a treatment plan for a small fee, refundable on your first purchase. Like others, I recommend panels made of rockwool (and fabric covered), rather than foam. It is far more effective acoustically, and it does not oxidize and deteriorate over time, which some foam does.

Three month wait? I understand, we all get impatient. But the payoff at the end will be far greater than slapping up a few foam panels.