> what are ETFs and/or financial products that take this into consideration?
They often have something like "Value" in the name, e.g. VTV, IUSV, SPYV. While not explicitly targetting now Shiller PE, they usually have significantly lower PE than "growth orienten" stocks (such as most of the tech megacaps that currently dominate SP500, VT and other market cap weighted funds). What exactly goes into "Value" funds is either too opaque or takes too long to explain in a comment.
> what difference does it make in terms of volatility and/or expected returns to invest in something like SP500 or $VT compared to Shiller-PE-adjusted products?
Volatility is likely (but not certainly) lower. Expected returns: convincing narratives could be told either way, but nobody knows with any certainty.
> does this matter in the long-term, or better, when exactly is "long-term" long enough so that Shiller PE doesn't matter and one can just go with SP500/$VT without sleepless nights?
Again, nobody knows, and you should be skeptical about pretty much any opinion that smells like investment advice. The posted graph shows that the current S&P 500 PE (or some approximation thereof, SP500 didn't exists until the 1950s) is high by historical standards. What to make of that is open to different interpretations.
Many people might intuit some sort of mean-reversion process behind (Shiller-)PE, but
- it's unclear which to "mean" and at what time frame it would revert
- as another poster pointed out, mean-reversion could take place by E going up as well as P going down
For the OP, if you are looking for a classic on "value investing," Benjamin Graham's "The Intelligent Investor" will lay it out. I invest broad index rather than value, but it's a good read.
They often have something like "Value" in the name, e.g. VTV, IUSV, SPYV. While not explicitly targetting now Shiller PE, they usually have significantly lower PE than "growth orienten" stocks (such as most of the tech megacaps that currently dominate SP500, VT and other market cap weighted funds). What exactly goes into "Value" funds is either too opaque or takes too long to explain in a comment.
> what difference does it make in terms of volatility and/or expected returns to invest in something like SP500 or $VT compared to Shiller-PE-adjusted products?
Volatility is likely (but not certainly) lower. Expected returns: convincing narratives could be told either way, but nobody knows with any certainty.
> does this matter in the long-term, or better, when exactly is "long-term" long enough so that Shiller PE doesn't matter and one can just go with SP500/$VT without sleepless nights?
Again, nobody knows, and you should be skeptical about pretty much any opinion that smells like investment advice. The posted graph shows that the current S&P 500 PE (or some approximation thereof, SP500 didn't exists until the 1950s) is high by historical standards. What to make of that is open to different interpretations.
Many people might intuit some sort of mean-reversion process behind (Shiller-)PE, but
- it's unclear which to "mean" and at what time frame it would revert
- as another poster pointed out, mean-reversion could take place by E going up as well as P going down