Indeed, I hadn’t considered the aspect of interest as this was not the main point in OP’s quest for optimization.
Taking this into account, it seems that Raiffeisen might be a better option. Depending on the region, Raiffeisen offers up to 1.1% on savings accounts, which is not only more attractive than what ZKB offers but also more advantageous than Yuh. Additionally, Raiffeisen provides great flexibility and extensive availability across Switzerland, as well as all necessary daily services, including joint accounts, mortgages, etc + the e-banking and app environment is working great.
I think it is possible to optimize even further by primarily using SwissQuote as a bank and broker. To my knowledge, SwissQuote’s debit card is the only card that offers a form of cashback as trading credit, which can be used to cover transaction fees for purchasing stocks, ETFs, etc (Yuh offer comparable privilege but missing the fact that you can’t have all the retail banking services with Yuh). In this sense, it would be, from a minimalist perspective, the most optimal account that allows both recovering cashback daily by using the debit card and paying abroad with a relatively low, albeit not optimal, conversion rate.
However, this only works if you exclusively use the SwissQuote debit card and do not use credit cards like Amex Cash Back or Certo. In this context, I think the Cumulus card would be the ideal backup credit card. However, this combination generates certain fees that would need to be covered with relatively high daily expenses.
I believe he is talking about the safety buffer, which explains the recommendation to keep 10,000 francs in a savings account.