I normally use Fedora with a theme identical to macos, but now since I have to use Windows for work I thought I would rice this as well. Below are the things I used for this rice.
Programs and things used:
Wallpaper: Greenfield City
Overlay, using a custom meter: image
Visualizer and Media Player: Jaxcore
Horizontal Menu and Clock: Big Sur RC1
UI Icon Theming: 7TSP
UI Icon Pack: MacOS Monterey
Icon Pack: Tile Icons
Also some custom and self-made icons from macosicons.com
Titlebar Theming: UltraUXThemePatcher
Titlebar Theme: LIT3
Cursor Theme: VS Cursor 11.0
Dock and Top Bar: MyDockFinder
Fullscreen Launcher: WinLaunch
Keyboard-controlled Launcher: Flow Launcher
Firefox Theme: WhiteSur
The best alternative to Rainmeter that is also cross-DE (Desktop Environment - i.e. you can use it on KDE, as well as Gnome, XFCE etc.) would be Conky.