Thanks for updating the thread.
You can have 2 banner that displays on desktop and mobile separately and hide the same using Hide During Breakpoints feature.
Regarding SEO, I don't think it should have any impact on the SEO. See, when I comes to SEO primary stuff that a webmaster should focus is the content which should be of high quality. Content is and will always be the king. Next, comes weather website is loading fine on mobile/responsive devices or not. Over here you are already in good hands as X Theme and Pro Theme are extremely responsive themes. Then comes the page load time which depends on a lot of factors. However, here also X and Pro Theme are very fast when it comes to load time.
All in all, I would suggest you focus on the fundamentals, make sure the content has right keywords that you think users are going to type, website is loading fast and SEO should fall in place. I also suggest you to take advantage to Google webmaster console. It's a free and amazing tool that you should use to get more insights on your website.
Here's a getting started guide.
To understand SEO more deeply and fundamentals of SEO, I suggest you to watch Google webmaster videos and especially one's featuring Matt Cutts (former head of Spam at Google). They are really nice and informative. For example, take a look at this video on the things a website owner can do to rank better. Please don't get mislead by the title, it's a good video:
To get some help on optimizing the speed of the website, please take a look at following article.
Hope that helps.