I very much like the idea with the top menu allowing to access most important pages directly from a menu bar. Also having the direct link to the own profile etc. would probably save us a lot of additional clicks on the hamburger toggle menu.

Not sure about removing a panel and/or changing the existing page structure though. I like the current width of the center panel, which allows to see the important content without moving my eyes from left to right. So, when scrolling down per mouse, I basically don't need to move my eyes very much and this makes exploring the content very comfortable to me.

If the standart setting would be like it currently is, but the left and/or right panels would be collapsible/resizable, I would see that as a good compromise between both worlds. For pages other than the user profile I prefer the version with only tabs and without the profile header.