Tool lazy to read it all with existing comments but still want to help so :
Recommendations for Notepad++ replacement
vim/gvim (and derivatives, e.g. neovim) or emacs or derivatives, if you are serious about text editing, being text or otherwise, they are the foundations. They probably include most of what you need out of the box and if not they do and a lot more through their extensions
I have an iPhone, I like to back it up and sync
You are swimming upstream there. Apple is doing everything it legally and technically can to lock up its own ecosystem. You might managed few things with e.g libimobiledevice/ifuse or ish or even KDE Connect
I do some gaming.
Me too, playing both 2D and XR on a nearly daily basis. It works. Sadly, just like the previous answer some are trying to sabotage anything they can via DRM or “anticheat” and this might screw up your experience entirely. A good heuristic is if works on the SteamDeck (cf ProtonDB) it probably works on Linux.
How do Xbox One controllers work wired with Linux?
They work. I don’t have an Xbox controller but SteelSeries ones and I play near daily on them, either with their dongle or via BT, with Steam or anything else.
Recommendations for GUI mpv frontend?
VLC
I use software called AdvancedRenamer.
As suggested in the first answer, learn Bash or any other CLI environment, it’s made for this kind of tasks and is the de facto standard for literally.
Keyboard shortcuts.
They work. If you need more it takes second with your desktop environment, e.g KDE Plasma for me, to add new ones.
I don’t understand Linux distro segmentation especially when it comes to software availability
That’s the “cost” of freedom. You do whatever you want with your computer. It sounds trivial but it’s not. We have been trained for years if not decades to see someone else get to decide for us. It’s false. It’s amazing. It is also daunting. Now YOU get to decide. You can use you distribution package manager or a binary or… anything in between (AppImage, AM, dbin, cloning a repository and building from source, etc). It’s crazy… but it works so it’s up to you.
Last but not least. I’m looking for suggestions for a Linux distro to use that fits my needs.
Who cares, picks any one BUT keep your data safe! Try it for an hour, a day, a week and try another one if you feel like it. Switch whenever YOU want for whatever reason YOU care. Cf previous answer.
Well, arguably it’s difficult at first then become much easier BUT I understand one might not want to dedicate time to it. There are solutions though to buy hardware that is open hardware and with open-source firmware. I personally do NOT recommend reverse engineering except for the pursuit of knowledge. I do NOT recommend RE for “liberating” products because even though it is amazing, it is adversarial. The companies are making money still while NOT supporting Linux or even preventing it from being supported by the community without them spending a cent. That’s fine, that’s their strategy. I don’t approve of it but from a business standpoint I can understand it.
What I do recommend though is spending few minutes looking for proper alternatives. I clarified that a bit in another thread about inputs, cf https://lemmy.world/comment/12550034 so please consider having a look.
TL;DR: DIY/RE can be too much work but there are open hardware with open-source firmware projects sold on e.g https://crowdsupply.com which are “just” plug&play.