Using the mouse to switch to a given program in the take bar isn't necessarily slow. It's actually faster if you have a decent number if windows open; clicking on exactly the right one straight away is faster than repeatedly pressing Alt-Tab and seeing if the new window brought to the foreground was the right one.
One of the things that made multitasking on Windows much better for me was discovering that:
1. win+<number> opens the <number> program on the taskbar from the left. So having a bunch of pinned programs makes opening them very fast and easy.
2. Holding the windows key down then pressing the number multiple times allows switching between multiple instances of the program, similar to holding alt and hitting tab multiple times.
For example, chrome is the tenth icon pinned to the taskbar (counting from the left). So win+0 open chrome or if already open switches to the first window. Holding the windows key and hitting 0 allows me to quickly switch between multiple chrome windows.
So I don't have to mentally keep track of the current alt-tab order to switch between the second putty window and third chrome window. I just hit win+77 for putty and win+000 for chrome.
Im sure you know this but in Windows 10 if you hold down Alt after hitting Tab the first time it’ll display which windows you already have open, and hitting just Tab again will cycle though them. You can even hold down Shift as well to cycle through the list of icons but in reverse.
I'm sure you know this, but, I think at least since Windows 7, while having the Alt+Tab "popup" open, you can use the arrow keys while holding Alt down to directly navigate to the window you want to open. Very useful if, like me, you have 20 windows of browser tabs open, and the application you want is in the middle of the list.