Hi Tony,
Welcome to the Forum.
I'm not entirely sure about the Power Menu (Windows Key + X, or right-clicking Start), but as you mentioned this has happened with other programs too, then it is plausible a shell extension which is how an installed program adds itself to your right-click Context menu, may be the culprit.
You can use a tool developed by Nirsoft to see what shell extensions you have, and disable all of them, then one by one enable them to test whether when one is enabled whether the lag in population of the menu appear. If it does then you simply disable that shell extension for now, problem sorted.
There Is a blog on this here:
https://www.raymond.cc/blog/fix-for-very-slow-or-hang-when-right-click-on-a-file-or-folder/ that makes a better explanation on the issue.
Nirsoft's website and link to the Shexview tool is:
http://www.nirsoft.net/utils/shexview.html
So far as the right-clicking on Start and the power menu taking time to load. Do you have Cortana enabled at all?
Cortana has for some Users been buggy and its SearchUI.exe has caused symptoms like you describe in the past.
The location of this
SearchUI.exe is here: C:\Windows\SystemApps\Microsoft.Windows.Cortana_cw5n1h2txyewy
Some Users renamed the SearchUI.exe to work around this issue, as once renamed Windows cannot find it.
However, in Windows 10 Creator, you need to change permissions to be able to rename it, as its owned by the SYSTEM's TrustedInstaller.
Others in the Forum may know more on this issue, and hopefully will reply to your post too.
Regards,
Regedit32