'Always show bookmark bar' is the top item on my View menu.Sure, you can change the default easily enough. I'm just giving an example where I do find it useful to have more Chrome displayed at the expense of a small amount of content area.
I can't comment on this I've not used a scroll bar since I got trackpad scrolling.
I'm usually working on a desktop PC, so I don't have a trackpad. I use a mouse scroll wheel all the time, but for long documents that's tedious (as is using a trackpad) and with most mice it's a one-dimensional scroll anyway.
I'm not clear what your complaint is here. Dev tools is too crowded?
Yes, and many things in it are far too small for comfortable use. The developer tools in both Chrome and Firefox are riddled with basic usability and design blunders, such as using tiny fonts and icons; using a flat design that blurs everything together and often gives no clues to what interactions are available; offering many different sets of tabs, icons and other controls; numerous inconsistencies in presentation, not just in the different behaviours from tab to tab but even from one set of tabs or icons to another that is visible at the same time; and forever moving things around, particularly making unnecessary minor changes every few weeks.
I've nothing against providing for developers who are using smaller screens, but I have a powerful computer on a real desk with nice big screens to make me as productive as possible, and the idea that everything must be crammed in to maximise the content area at all costs just isn't helpful in that context. Rather like the perversion of the original "mobile first" design idea to become "over-simplified least common denominator behaviour is good enough", it's throwing the baby out with the bathwater and actually making the software worse for some users. Of course the developers of these browsers are perfectly entitled to do that, but it's equally fair to point out the problems they are creating.