Blog entry layout

Good evening,
Sorry to repost this question, but I’ve been trying out many plugins and pieces of code to get what I want. They all involve creating a page which includes short code, and I’d rather stick with this theme’s structure.
I managed to get the right size of thumnails in the home page post listing using this custom CSS code I found on this forum:

.blog img.attachment-post-thumbnail.wp-post-image.img-responsive, .blog .entry-content .thumbnail-post .mask, .blog .entry-content .thumbnail-post div.icon, .blog span.thumbnail-post {
max-width: 200px;
}

It works for the home page listing, but how can I apply the same solution when the page lists posts from a specific category?

I’m also trying to have a blog listing layout where the thumbnail sits at the left of the post exert and meta. That too, I’d like to achieve without adding another plugin.

Thanks for your help!