[Support request] How many queries on one page is too many

Hi,

I am making a private dashboard for authors with all there own content accessible.
There are multiple areas – slide in and out sidebars and the primary area, where their previously created content is sorted into categories.

I thought it might be faster to create a template with just one loop and get each category from within the one loop.
Or is it fine to have multiple wp show post calls per page?
Finally, the wp show post shortcode for each item is first being run through a snippet to get the userid and limit the posts shown.
What am I up against in terms of scalability. How many items can I include before the page loses its mojo. Already after 3 custom queries it’s a slow load.
Can I use one wp-show-post and get all the different cats from it in one loop?
Please forgive my hack approach!