Let’s say I have created a page with a group with a specified width within which is all my content (paragraphs, featured image etc). I’d assume these ad inserter plugins can insert the ad code into the paragraphs etc within this group block.
Sure. You can define rules like “place an ad after every X number of paragraphs”. Using paragraphs as a marker is just an example. Different plugins will have their own criteria.
But let’s say I want ads to show outside this group on either side, can these plugins do that cos the page itself by design wont have any defined space to add any more blocks outside this group?
I’m not sure what you mean by “group” in the context, but I’m supposing you mean outside the post/page content area: eg sidebar, header, footer, before post, after post, on archive pages, etc. If this is what you meant, I actually touched on this earlier when I said:
… you can’t manually insert ads into some sections of your site (eg in-between category/date/tag archive listings, above post title, etc) without custom coding.
So, yes, the plugins can do this automatically. You’ll just have to configure and define the ad zones where the plugin should display the ads. And you’ll likely need different AdSense codes (with different dimensions, unless you’re using autoads).
But if you just want to Google to automatically decide where and when to show ads (and what ad sizes and formats to show), then just install and activate the Google Site Kit plugin, and connect it to your AdSense account. Google will take care of the rest.