MenuMeters works fine on my Mojave, but from reading release notes it would appear to run on BigSur as well. MenuMeters for OS X El Capitan 10.11 and later https://member.ipmu.jp/yuji.tachikawa/MenuMetersElCapitan/ and https://github.com/yujitach/MenuMeters

I've been extraordinarily happy with iStat Menus for showing a variety of system info in the menu bar.

https://bjango.com/mac/istatmenus/

I used the MenuMeters forks up until a few months ago when I purchased iStatMenus. Love it and well worth the money, especially since I can used the unified view (so my widgets don't get moved around arbitrarily by menu bar reorganization).

One thing I recently discovered is that macOS has no capacity to deal with overflow of the "menu bar widget" area.

I had rotated my 27" 5K displays to portrait mode, which I find better for coding. That made the menu bar narrower. The widgets in the menu bar on the left side just don't appear when the frontmost app's menu is too wide.

Since I use iStat Menus for this purpose, which puts (in my configuration) 6 different widgets there, and have several others as well, lots of icons were simply inaccessible.

That is one argument for Pluto's approach here.

I'm not certain I know what you mean, but have a look at https://bjango.com/mac/istatmenus/

Give it a try, we think its a lot nicer than the tiny menu bar stats most apps provide -- they just don't display the right amount of information.

You can quickly collapse it away when you want it out of the way by clicking on the left mode "PLUTO" label.