Trading currency of ETF doesn’t really matter. Much more important what’s inside. You can buy S&P 500 paying CHF, USD or EUR, doesn’t really matter, it’s still the same basket of stocks in the end. There is no extra currency risk added by just buying it in a different currency at spot rates; currency risk is in the composition of its holdings.
Except if you buy currency-hedged ETFs - then besides the basket of stocks you’re also buying currency forwards and then the currencies matter.
In case of equities also important the revenue exposure of companies. Nestle is a swiss company, quoted in CHF on SIX, but they make only ~ 1% revenue from Switzerland. It’s not swiss at all from this perspective, but a global conglomerate that just happens to be headquartered in Switzerland for historical and tax reasons. In case of a massive appreciation of swiss frank vs. rest of world, everything else equals, it’s a sure thing Nestle’s revenues are gonna get hurt and its stock price in CHF is gonna crash - its currency risks are in revenues exposure.