The best post about performance in my opinion is this post: http://www.stukkie.nl/mendix/the-developers-guide-to-performance/ by Stephan Bruijnis.
Regards,
Ronald
Generalisation does impact performance. If it's causing your specific issue is hard to say without any context.
This article is useful: https://world.mendix.com/display/bestpractices/Inheritance+vs.+1-1+association