The basic rule is that the electronic modes typically offer the best exchange rates.

Anything involving paper or an exchange booth comes with higher transactions costs.

Minimizing the number of ATM transactions cuts associated costs, and minimizes exposure from malfunctions/nonoperations.

One can always carry $300 in US cash or so to cover any contingencies.

My view is that travelers checks are completely obsolete. The last place I used them, in Tanzania (no ATMs at the time), there was a 3% charge from the merchant for accepting them.