RCA Shorting Plugs vs Caps non-shorting ?

I have had Cardas RCA Caps on all unused inputs in my preamp for some time. I recently bought an inexpensive bunch of gold-plated Chinese RCA Shorting Plugs on eBay (Cardas has a much more expensive version). The Shorting Plugs had a dramatic impact on dynamics seemingly reducing the noise-floor. (I seem to remember that back in the 60's/70's, shorting plugs often came with the preamps and integrated amps I had then) Are there RCA jack locations that can only be served by Caps vs Plugs? The second Preamp Out and Tape Out would be candidates for Caps vs Plugs, but all other unused jacks should take Plugs. Is that correct guys?
Shorting plugs should only be used on inputs
Good move Elunkenheimer, I did the same. A dozen true shorting plugs on ebay for ten bucks I think it was, much cheaper than the price of the Cardas plugs, which do nothing but keep dust out of RCA jacks. Big deal.
Yep, all Cardas does is reselling 10...20x higher to naive consumer.
Caps are best shorting plugs not so great.
All unused RCA plugs should have caps, including video Inputs and outputs, even the TV unused inputs and outputs. Apologies for being mysterious. One note: the caps allegedly prevent EMI/RFI from entering through the open plugs but if you do the math the diameter of the opening is too small for almost all electromagnetic waves.
Thanks so much for the responses guys. To be clear: Rello your suggesting that shorting plugs be put only on Inputs and on no Outputs. So "Tape In" would take a shorting plug, but "Tape Out" can only take a non-shorting Cardas cap,same for a second "Preamp Out". Geoffkait you referenced the application of non-shorting caps, but not shorting plugs. Do you agree with Rello and my summary?
I never used shorting plugs so cannot say yea or nay. To reemphasize my point that using caps on unused inputs and unused outputs of the TV or unused gear in the room should improve the sound. This is because the caps don't have anything to do with EMI or RFI.
At one of the Bill Johnson in-store appearances I attended, he told the story of a problem caused by shorting plugs. ARC had sent a pre-amp (SP-10?) to Harry Pearson for review, and soon heard from him as he was having an issue with it. The problem was traced to Harry's installation of shorting plugs into the pre-amp's output jacks. Harry's lack of basic electronic engineering knowledge had once again caused a designer/manufacturer grief!
I've had subtle improvements using RCA shorting plugs on unused audio inputs. But rather poor results in some, but not all unused video inputs. Maybe the video problems occurred because adjacent non-RCA (S video/component) inputs for the same video input were being used, or maybe because there was an impedance mismatch? Perhaps not a problem with most of todays current DVI/HDMI inputs?
Seconding the comments by Rello and Bdp24, if you were to put a shorting plug on an unused analog output, you would be stressing the circuit which drives that output, by causing it to supply a greater than normal amount of current. Whether or not that would affect long term reliability, as well as functionality and sonics, would depend on the design of the particular circuit, including its output impedance.

Also, if you were to put a shorting plug on an unused second main output of a preamp, since most (but not all) preamps which provide two sets of output jacks simply wire the two sets of jacks directly together inside the rear panel, doing that would kill the signals at the output that is being used. Perhaps that was the reason for HP's problem that Bdp24 referred to.

And depending on the specific design shorting a tape output might also affect the main signal path.

If you want to consider putting something on unused RCA video or digital audio outputs, what should be done is to apply a 75 ohm termination. I don't know if that would make any difference, and I would not expect any difference it may make to be consistent from system to system. 75 ohm terminations are readily available inexpensively in BNC form, since they are widely used in pro applications. But the RCA versions I've seen, which are marketed to audiophiles, tend to be absurdly expensive. If you can't find an RCA version costing say a few dollars, you might consider either making your own, or else using a BNC version (as shown here) together with an adapter (as shown here).

-- Al