Simply Automated Devices

Single rockers are easy, there are multiple brands that work well with smartthings, including Leviton, Cooper, gocontrol, GE, etc.

https://www.amazon.com/Leviton-DZ15S-1BZ-Decora-Switch-Technology/dp/B01MZ0WVKH/ref=dp_ob_title_hi

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https://www.amazon.com/LINEAR-GoControl-WS15Z-1-Zwave-Switch/dp/B00E1OQN8Y/

See the device class features FAQ for more details on selecting switches. The light switch discussion starts around post 40 in that thread.

As far as the two switches in one gang, currently the in-wall micro is the only option for that: