Your widgets should work fine visually while streaming to multiple sites at once. The problem that you may run into is that many widgets for streaming such as Alert Box and Tip Jar are configured to work with either Twitch or YouTube but not both at the same time. A solution to this problem might be to create two separate browser sources within OBS, one for YouTube alerts and one for Twitch alerts. This is something to keep in mind while multistreaming with widgets. Or, you can find other widgets such as countdown timers that do not require integration with YouTube or Twitch. These widgets might be more appropriate if you are regularly multicasting.