The last time I was there in 2022 there was free passage between the French and Swiss customs areas landside, on the arrivals level (lowest). In theory it is a customs control point but I and others wandered back and forth multiple times, and so even if you went took the 'wrong' exit when arriving it wouldn't have been a big deal.

The landside shops use CHF on the Swiss side and EUR on the French side, but it seemed that airside operates in euros only (I guess they would take Swiss cash at their own exchange rate).