We don’t really know exact print run numbers, but it’s generally accepted that for all eras Japanese cards have lower print numbers than English cards. Most of what we know for print runs is very relational (i.e. Japanese ex series is the lowest print run, Japanese e-series 1 has more than the later e-series).
However, Japanese cards also have different pull rates, so there’s some variation there in terms of “rarity” if that’s what you’re looking for. Japanese neo-era Shining cards were very difficult to pull, while the English ones were comparatively not as hard. In XY7 Bandit Ring, Ultra Rare cards (especially the shiny Primals) are much more common than they are in English.
I would caution you on assuming that a lower population report and lower eBay listing number reflects card rarity. Often enough this just means that there isn’t as high of an interest in the Japanese cards. For the vast majority of set cards, the English printing has the most interest and that will lead to the most market activity (e.g. grading, listing, visible sales).
Let’s keep this discussion to the rarity/print numbers. If you want to discuss whether something is undervalued or not, do so in the Giant Market Thread here: www.elitefourum.com/t/the-giant-english-market-thread/27424/1