How do I remove and/or change the speed of the minimize animation for application windows in macOS Catalina?
I do not know of a speed setting for this action.

That said, the default setting for the Dock preference Minimize windows using: is Genie effect and the Scale effect may be a bit faster, so I'd try that one.

There is also a Suck effect, which can be implemented via Terminal, using the following compound command:

defaults write com.apple.dock mineffect -string suck; killall Dock


Note that after using the above compound command you will not see Suck effect as a setting for Minimize windows using: as a Dock preference, however using the following command will show  the present value, e.g.:

% defaults read com.apple.dock mineffect
suck
%