...do you recommend creating in widescreen or standard?
OK, flippant remark aside, you create in whatever dimension you want. The cool thing about the web is that you're not bound to any particular frame size or aspect ratio. Let the project and/or content dictate the output, not any generally-accepted convention.
Welcome to the forum.
With few exceptions, one should set their Project Preset to match their source footage. Are you starting with Widescreen, or Standard? That will be the determining factor.
The possible exception would be if you ONLY have still images. In that case, one would determine the intended delivery format first, and then Scale the stills to match that. You still do the matching, but instead of letting the pixel x pixel and PAR determine the Project Preset, you adjust your stills to match the Project Preset.
Can you tell us all about your source footage?
Whatever you want, widescreen is fashion these days as HD only comes in widescreen.