1- Laptop macbook pro with m1 pro. I also have a ThinkPad L13 gen 2 as a backup.
I mainly use laptops because I like the portability: I don’t have a single place where I use these computers. I prefer the macbook because it runs my preferred OS, which is macOS.
The monopoly Apple holds on the repairability of the macbook makes me uncomfortable, which is why last time I was switching laptops I went for the ThinkPad with Linux, but I realised I was less productive than with macOS, so I ended up buying the macbook after a year. (I use the computers mainly for work)
2- My preferred OS is macOS because I find it a more polished and pleasant user experience compared to Linux and Windows both in terms of the OS and app ecosystem. Linux had some compatibility issues with my USB-C monitor. I also prefer the security model of macOS.
3-The main app why I’m more productive on macOS when working is Dash. The speed with which I can quickly jump into the official documentation of something very specific and on the relevant version makes me work differently than the usual approach of searching for it online, as there are way less hoops to get to the official documentation, and way less chances to end up in a Stack Overflow (SO) question. So it’s not only quicker to get to what I want to, but also since I almost always read the official documentation, I learn more about the tool than copypasting answers from SO, which means that I become more versed on the tool quicker. I feel like Dash has made me and keeps making me a better developer. I’ve tried alternatives like Zeal and DevDocs in Linux, and they sort of do the trick, but nothing compares to the versatility of Dash.
As for browsers I use Firefox for “browsing around”. I use it with uBlock Origin (uBO) in hard mode + noscript for blocking media. I downgrade to medium or easy mode of uBO with a keyboard shortcut until the page I’m visiting is usable. For serious stuff and important accounts, I use Safari in private mode without any plugins. When I’m going to buy anything, or looking for something to buy, I look for it using the Tor browser to avoid price discrimination, and once I find it, I’ll move to the other browser (probably safari) to buy it and if the price differs in a consistent way (I can see both prices simultaneously even after many refreshes), I’ll never use that provider again (good bye booking.com).
I mainly use the browsers rather than the apps, unless the apps give me some OS integration that I find valuable for my specific use case.
For password manager I use 1password, as I find it a more pleasant UX than Bitwarden and I trust them and their audits.