The Lounge is rated PG. If you're about to post something you wouldn't want your
kid sister to read then don't post it. No flame wars, no abusive conduct, no programming
questions and please don't post ads.
Well, they're targeting people who are daft enough to pay them a fee every month for storage that costs next to nothing, if it's sitting on the desk, so they have to use terms appropriate to that audience.
I wanna be a eunuchs developer! Pass me a bread knife!
I don't know what kind of machine you're working on, but I really have more than enough system resources available that a transparent bar here or sliding animation there in my OS do not make a noticeable difference in overall performance. If you don't like the modern look, that's fine, personal preference and all, but the argument about system resources being wasted seems pretty out of date in 2017, unless company politics force you to work on a toaster that someone soldered a VGA port on.
For screenshots, I'd see it as far easier to just turn off transparency, because that's the only thing I can think of that might influence the result of the screenshot, depending on the background.
That way, you also don't get the "but my screen looks totally different!" support calls from the people you make the screenshots for and who might not be using that theme. You wouldn't believe what non-tech-savvy people get stuck on.
Also, if anything makes you look professional, it should be your skills and results, and not your toggling a setting for Office or which theme you chose for your OS.