Importance of power cable for Turntable?

While all this thinking about noise from/to the table may be true (or may be better addressed by other steps as the OP suggests) my experience is that even when the AC is treated (as in my system) by multiple levels of filtering well before the power cord to the table it still is the case that changing the power cord to the table adds benefits. The effect is similar to a good power cord on an amp -- more stability and attack, more ease as the table is subject to wide dynamic swings, a crisper presentation etc.

All of this is icing on the cake in an optimized system but if that's where you are heading, and you have a power cord handy, do try one -- the effects are likely to be additive to whatever else you are doing (and that's before getting into the benefits of footers and other vibration control effects on the TT PSU as well ...)

Of course I may well be totally lost in tweakery woo land ... but that's the territory we're operating in now

Wow!  Okay I’m hoping not going to quite that crazy with power mgmt lol!

Have to point out the slight irony in all of your power mgmt lengths you have taken but use a stock cord to the turntable!  Probably makes sense though.

nyev it doesn’t work quite the way you think. Having everything on one circuit almost always turns out to be better, especially with a turntable where the greatest source or risk of noise is hum, which usually comes from different ground potentials. Also nothing really isolates from anything else. Oh, to a degree. But we wish it were so easy.

No idea what table you’re looking at, but the realm you are in with what you mentioned so far, you should be looking at a lot more than a power strip to plug into. You can do a whole lot better than a 8D, which is basically just a power strip. A good power conditioner, everything plugged into it benefits.

And yes, great lengths in power conditioning only to use a freebie cord the last few feet is ironic. It makes no sense. At all. DYODD.