It's hard to speak specifically about those beers, because I haven't tried the two UFO beers you've mentioned. I have had Paulaner Weiss but I don't remember how it tasted
The banana flavor you are tasting is known as isoamyl acetate. It is a byproduct of the yeast used in fermentation. Different yeasts will result in different amounts of this flavor, and they should be carefully selected for their ability to produce it. There are three popular ways (that I know) of manipulating this flavor. The first, is by manipulating the mash. Conducting a decoction mash causes a difference in enzymatic activities that allows the yeast to become diauxic, whereby it produces more esters by increasing acetyl CoA production. The second is by increasing the temperature of the fermentation, which also has been proven to increase acetyl CoA. The third is by reducing wort aeration, which similarly increases acetyl CoA. Essentially you are doing everything in your power to stress the yeast and decrease its ability to grow/reproduce.
There is a fourth way, which is increasing the gravity...but normally for a wheat beer you're not looking for a really high gravity anyway.