You can turn the ajax style by going to home page options (assuming the showcase is the home, front page) and setting 'Load Slides Content With Ajax' to 'No' (see Portfolio Showcase Template tab)

For your first request you need to go to portfolio-showcase-page.php and set 'posts_per_page' => 6,

on line 39

Thanks

Hi yes,

think of the showcase template as a different view of the same set of portfolio items.

you can control which projects are being displayed in it by modifying the query selecting the projects

portfolio-showcase-page.php

where you set the parameters

$bario_args = array(
'post_type' => 'bario_portfolio',
'paged' => $bario_paged,
'posts_per_page' => 1000,
);

see

https://codex.wordpress.org/Class_Reference/WP_Query#Post_.26_Page_Parameters

'Display only specific posts'

for example

$bario_args = array(
'post_type' => 'bario_portfolio',

'post__in' => array( 2, 5, 12, 14, 20 ),

'paged' => $bario_paged,
'posts_per_page' => 1000,
);

Thanks