UI/Design seems attractive. This is a Open Source wallet? Can you please share link if it is?
The fee mentioned on the buy crypto page is Fee: 7 USD* is this fee is fixed or fluctuate?
It is partly open source since there is no fully open source crypto wallets,AFAIK. For your first question you can check the this reference by thread manager to similar question:
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We intend to reveal the code. Partly. When the product is closer to what it's meant to be, with the enterprise and dev functionality, and most of the options for users are implemented, so that we have what to show indeed

Once again, there are no fully open source wallets: if it reads 'open source', it doesn't mean you'll see something but frontend opened. At least it's true for more solid, multifunctional products
The fixed fee is applied for buying crypto with OWNR wallet but the additional fee or bank commission can be charged by card issued bank. For getting more information check this video:
https://www.youtube.com/watch?v=T2ItC7yQTYg&feature=emb_title