AMD Drivers: if your GPU is new enough (which it probably is since you're playing Star citizen) it should be just magic here since they come together with the kernel.
Chrome: it's available for Linux, no need to switch. Although Firefox is very nice too.
Gmail: not sure what you mean, Gmail is a website, those are available on any platform. If you meant a desktop email client (which honestly I have never in my life used) there's Thunderbird.
Office 360: Are you talking about Microsoft 365? Is that not a website too? In any case Libre office is a nice alternative to the classical Office desktop app too in case you want that.
I-Tunes: A quick search online reveals people use wine to run the Windows version of iTunes, although I would probably consider migrating. Spotify has a native client and there are some places where you can buy music and have it locally for playback.
JBL: not sure what this is other than a brand for speakers.
Anti-virus: You almost assuredly don't need an anti-virus on Linux, as long as you install software through the proper channels (i.e. using the package manager) chances of virus are so small it's not something to worry about. Most Linux anti-virus serve to check windows binaries in the system to avoid someone using the Linux machine to send virus to Windows users.
PyCharm: it's available for Linux
Remote desktop to iOS: Not sure this is possible even on Windows, I use remmina for remote desktop, it supports several ways of connecting to the other device so maybe see if it works for you.
Star citizen: Never played it but it seems to be playable with Wine.
Steam: While steam is available not all games are compatible, check out https://www.protondb.com/ to see the status of any specific Steam game.
VPN: should be native on Linux, there's a protocol caller OpenVPN which most VPN providers will give you a Config file for that you can use directly on the network applet on Linux.
PS: Next time share the list in text, it makes it easier to reply
For someone tech-savy and privacy focused - LibreWolf
Why? Some websites will not work properly on LibreWolf because of how hardened it is (not extremely, but just enough to break some things on websites). I don't mean it's bad, it's just not for everyone atm since many people want things to just work™
Remote desktop to iOS: Not sure this is possible even on Windows, I use remmina for remote desktop, it supports several ways of connecting to the other device so maybe see if it works for you.
What? This is absolutely possible, and it seems like OP is already doing so from Windows. Remmina is also, as far as I'm aware, a client app, not a server. I would personally recommend Sunshine, with Moonlight as the iOS client, but that's more geared towards gaming. xrdp would be my recommendation if OP is using the built in Microsoft Remote Desktop Protocol currently, as that will continue to work with whichever iOS client they are already using. Otherwise, if they're using VNC currently, I would go with TightVNC as there are dozens, if not more, iOS clients.
He said remote desktop to iOS not from iOS, that means he needs a client on his desktop to access the server on the phone. If it was android the answer is scrcpy but I'm not aware of any such tools for iOS (since I don't own an iOS device).
I mean, I did read what they wrote. Remote desktop to iOS. Sending the desktop of the computer, to an iOS device. Nobody calls the home screen of a phone a "desktop".
iTunes just doesn't work even for really old ones for just to put some music on iPod. Haven't tried with Wine 10 but I don't think that's changed. This is the only reason I keep a Windows VM with an old iTunes in it.