Hi David,
Pretty sure the answer will be no (as in they will be fine), but of course always backup everything first.
And you will find the download to the theme in your account here on this very page, click the Account menu and select ‘Downloads and Order’
(ps you need to Pro membership to have access to the theme!)
HTH, Dave
Dave is right, you should always perform a backup before applying major modifications to your Website. Technically BB plugin should be compatible with all WordPress themes and we are here to help if it doesn’t. Let me know if you can’t find the BeaverBuilder theme, I’ll have my teammate to check them out.