You can use Sauce Labs Platform Configurator to correctly configure the required test capabilities for your Appium and Selenium tests. It will generate code fore capabilities to use. For example, on selecting Api -> Selenium, Device -> Mac, Operating system - >Mac OS Sierra, Browser -> Chrome 61.0 it will generate following java code.
DesiredCapabilities caps = DesiredCapabilities.chrome();
caps.setCapability("platform", "macOS 10.12");
caps.setCapability("version", "61.0");
When usig QAF you can provide capability using property as below
driver.name=chromeRemoteDriver
chrome.additional.capabilities={'platform': 'macOS 10.12','version': '61.0'}
You can use different combinations as documented in setting driver capabilities.
If you want to run your test on different browser/os combination you can do it in config file. Here is the example configuration file
<suite name="AUT Test Automation" verbose="0" parallel="true">
<parameter name="chrome.capabilities.version" value="61.0" />
<parameter name="firefox.capabilities.version" value="55.0" />
<test name="Tests on Mac Chrome">
<parameter name="driver.name" value="chromeRemoteDriver" />
<parameter name="chrome.capabilities.platform" value="macOS 10.12" />
...
</test>
<test name="Tests on Windows Chrome">
<parameter name="driver.name" value="chromeRemoteDriver" />
<parameter name="chrome.capabilities.platform" value="Windows 10" />
...
</test>
<test name="Tests on Mac Firefox">
<parameter name="driver.name" value="firefoxRemoteDriver"/>
<parameter name="firefox.capabilities.platform" value="macOS 10.12" />
<test name="Tests on Windows Firefox">
<parameter name="driver.name" value="firefoxRemoteDriver"/>
<parameter name="firefox.capabilities.platform" value="Windows 10" />
...
</test>
</suite>