Well done extensions have the possibility to use preset layout or choose the framework to customize the fields by calling the classes that already exist in the framework, just to avoid these problems.
However, when extensions are developed without using a framework, they define the classes in CSS so that, on whatever site they are loaded, the graphics will always be standard.
I have never seen an extension developed using the classes of a specific template because this makes the extension incompatible for website that do not use that template. This is a strong limitation.
I am really very sorry that JA Megafilter is not compatible with the Yootheme Pro templates, we are talking about an extremely famous company for Joomla Template. In the forum I have found many users asking questions related to this incompatibility problem.
It is unfortunate to discover such an important limitation only after purchase. Exclusive compatibility with the Protostar template alone should be clearly expressed given the limited number of sites that will be compatible.
In any case, I requested a quote for a custom layout, I await answers from the support if at least it is a feasible paid service.
However, I remain very embittered.
Best regards,
Marco