This is off-topic, but:
I was interested, but it doesn’t work well with special things like factor investing (and I hope Finpension’s new suggestions are going to work, soonish). So, I’m not. But I tested buying, receiving dividends, selling on IBKR.
You can directly look at all the ETF traded on JPX’s website. Probably can’t go too wrong with iShares. TOPIX is a reasonable index (400 stocks, market-cap weighted, free-float corrected). Compare funds following that index on Tradingview.
There are also a lot of dividend funds (under “Japanese Equity (Theme)”), but that is not exactly a scientific factor.
I think, regarding treaties, it’s nearly the same. If you go to justetf.com and filter “MSCI Europe” with LU or IE domicile, the funds seem to perform about the same.
CH funds will win, since there is no CH WHT in the fund (and Switzerland has a massive 15% weight within MSCI Europe).