Plain HTML page / Getting Rid of all Bootstrap Responsiveness and decoration

Hello All,

I need to get rid of all Template add ons in a custom (Add Record / popup) page,
bacause layout is complex and I am failing to get this done using the built in designer.

What is needed is a table structure like tha (exLavarel) examples towards the end of
this post
https://asprunner.com/forums/topic/26806-custom-input-pages

Variant 1) - Cleaning up page contents in Style/Page Source
Has anybody found a way to strip a page of all bootstrab/template code (DIVs, CSS etc)
to just leave over plain html (and the logic to fill datafields)?

Variant 2) - Dummy/Empty Theme
Or is there any "dummy" bootstrap theme araound which contains emptyness for all
elements and if selected in Designer/Style just adds only minimal functionality?
How to install this into PHPrunner?

Kind Greetings,