The only time i think the wingless look looks decent, it on a lowered Mustang with deep dish bullitt wheels with 305series tires . I think it looks badass only then.
For a stock ride height stock wheeled Mustang, i would leave the wing off.
I tried it on my car and was 50/50 on if i liked it or not. I have the plugs. I got them at home depot. They have them in the bins in the bolt aisle in the nylon plug drawer. 3./8th and 5/16th. Paint them with a little touchup paint and use some clear silicone when you install.
Be warned, sometimes there is a stain under the spoiler posts. Your car is new so it may not be there.
Next time i go to the track. i'll yank the wing. It literally takes 5 mins to take off with an 11mm nutdriver and i just pop the plugs in without silicone as long as no rain is in the forecast.