Thing is i'm playing around with the features to see what it can or cannot do.

That's cool -- if there are a set of specific requirements your assessing the platform for, it might be beneficial to share them with us as we can help you understand both whether or not Liferay can handle it out of the box,  and also possibly point you to the part of the application that would be used to manage it. 

So if we can move on from there,  I've also tried changing the success page to something like https://www.liferay.com/c/portal/logout which of course didn't work as well. Puzzles me that the page doesn't seem to actually load but changed static-ly instead (not sure how to say this better).

That won't work because that particular URL you are using is wired to a struts action that simply terminates the session (logging out the user). Once it is done, it routes the user to the default.logout.page (you can set this in the Control Panel > Configuration > Instance Settings section, or in the portal-ext.properties file -- though I would recommend the control panel as the value there overrides anything in the properties file). That can be set to whatever page you like (that you create) such as a /goodbye page. If you don't specify a page in that setting though, the system will automatically route you to the default home page. Portal level struts actions can be easily identified because they start with /c and, for all Liferay ones at least also contain a sub path of /portal .. hence /c/portal. The concept of pages in Liferay is very much a "virtual" thing since there is no physical file representing a page -- so we do talk about pages, but they are basically as much "routes" as they are pages. 

Or  if you could help me on the trailing question on how to remove the top and side panel (via .ftl theme template) would be great. I tried to hide  <@liferay.control_menu /> but some other part is still pushing the view down via css. I tried changing in init.ftl as well so it doesnt add certain logged in CSS but to no avail. 

Are you creating your own custom theme? By default the left bar is hidden unless you pull it in (at which point it will default to showing until you hide it again of course). The top bar is another story. Normally what I do for that one, in my custom theme, is change the CSS to put it off screen (negative position) and then in my own header I introduce a control that can be used to pull in down. That control is what I scope so that only users in certain roles have the trigger to do this. This way, the top and left bars are never visible unless, say, an administrator chooses to reveal them. But even if he/she does, it only makes them visible to the admin. 

Lastly, in case you didnt notice im trying to do this without using hooks or making any changes via source. More looking at it as configuration or theme development, to see if its feasable or not.

There is SO MUCH that Liferay can do out of the box, and in fact, there are usually many ways to achieve a specific goal. I would say tht if you can make something happen, cleanly, without having to extend of override something in the core product, that is you best approach of course as it simplifies the upgrade path to newer versions etc. With that said, part of what makes Liferay so powerful, imho, is that you can change almost anything that comes out of the box to meet your needs. Hooks and Modules are incredibly powerful, so I wouldn't rule them out completely. 

As I said above, maybe a list of requirements that you are using to assess the product is the best way to answer your questions. Like the logout scenario, you may end up asking how to do something a certain way because it feels right, but someone with more experience with the product (monitoring these forums) may point you in a different direction to achieve the results you need.