Is it possible to Authentication windows sdk using username/password?

You can login directly with credentials with:

LoginParam4Email emailParam = new LoginParam4Email();
emailParam.bRememberMe = false;
emailParam.userName = "Your email here";
emailParam.password = "Your password here";
LoginParam param = new LoginParam();
param.loginType = LoginType.LoginType_Email;
param.emailLogin = emailParam;
SDKError sdkErr = CZoomSDKeDotNetWrap.Instance.GetAuthServiceWrap().Login(param);

You can mute/unmute your mic after joining a meeting by using the Audio Controller and UserId 0:

SDKError sdkErr = CZoomSDKeDotNetWrap.Instance.GetMeetingServiceWrap().GetMeetingAudioController.MuteAudio(0, true); //Or false

You can mute/unmute your video after joining a meeting by using the Video Controller:

// To unmute your video
SDKError sdkErr = CZoomSDKeDotNetWrap.Instance.GetMeetingServiceWrap().GetMeetingVideoController.UnmuteVideo();
// To mute your video
SDKError sdkErr = CZoomSDKeDotNetWrap.Instance.GetMeetingServiceWrap().GetMeetingVideoController.MuteVideo();