I use both my PC and iMAC every day. Primarily Adobe Photoshop/Illustrator or other developer work on iMAC, which I prefer over WIN platform. And enterprise stuff like MS360, or Adobe Premiere Pro/After Effects (Video) on DELL WIN10 workstation, as it has faster processors and can accommodate Adobe's recommended nVidia graphic cards internally, which essentially can blow the iMAC out of the water.
For travel, I tend to take a MS Surface Pro or DELL XPS Ultrabook, both WIN10. But at home, prefer my MacBook Air.
I would definitely buy an external HD drive for backups on iMAC or PC, most any brand will do. Though, IMO, iMAC has a far better backup/recovery system "built-in" than WIN. If your internal drive fails in your iMAC, you're likely not going to be able to replace it unless you're a techie with specialized tools. About all you can do is upgrade the RAM yourself, not too difficult for most users. But then again, you will also have access to walk-in support from Apple stores.
You can install WIN on iMAC with Apple's free Boot Camp. Parallels is a paid app. Though, one caveat, a WIN or MAC OS upgrade can cause Boot Camp to fail on your system, requiring a restore. Another reason you should make sure to have backups.
I also prefer using a separate wireless mouse on my iMAC, which is actually a Microsoft ergo mouse. :B But works better than what comes with the iMAC.
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Another very handy accessory has been this inexpensive hub, which adds USB3 ports and/or SDHC card reader to the front of my iMAC. Especially, convenient for portable flash drives. It works very well, attaching to the vents on the under side, though need to make sure the screw is on firm. But will not scratch the case. I bought mine on Amazon.