Can I uninstall apps in Lollipop without clearing data?
Force stop &rarr; clear data &rarr; uninstall is the same as uninstalling app directly as far as removing app data is considered. It's just an extra step with no added benefit. 
Force stop option is primarily to troubleshoot apps when they misbehave
Either method does not guarantee removal of all app data - you would need root to ensure that. See Can a app store data beyond uninstallation?