Do you have page load times tagged in your website for every page? Page speed usually is a function of synchronous scripts , html rendering on the page, external resources requested(images, fonts, css) and resources afforded to the website by the browser. Asynchronous scripts which are there to measure performance or analytics have a minimal role to play , if any.
Loading the launch script itself should not impact page speed and if at all then barely.
If you are loading it in the asynchronous manner on top of the page and ensuring all third party and adobe analytics tags are executing on the page after page load is complete(this part is critical) , then there shouldn't be any issue. I'll suggest run an audit - how many tags are loading "on top" of the page.
If you still feel about page speed you can have the launch script loaded on bottom of the page. But , then no tags which have the dependency to run on top of the page(like adobe target) can run without some workarounds being added.