Decision time: What to use for screen captures with automated edits after capture?

I need a program that will do the following after a keyboard shortcut:

1) Take a screen capture
2) Apply a default edge to the capture
3) Scale to 800x600

Then, easily add transparent PNG symbols to the capture
For example symbols that look like hand drawn arrows, circles, etc., like this
https://www.techsmith.com/snagit-accessories-stamps.html

TechSmith’s SnagIT for Windows does this beautifully. But the Mac version is crashing on Sierra. I need something that works now.

 

@satcomer , yes I have that Mac keyboard shortcuts page bookmarked.
I also have printed out this page from someone else's post
http://macmost.com/downloads/MacMostKeyboardShortcutsYosemite.pdf

Also, I've moved the "screenshot" icon onto the touchbar so it's almost always there.

But what I'm looking for is a utility / tool (paid is good) that does all 3 things:

1) Take a screen capture
2) Apply a default edge to the capture (like a torn paper edge, a shadow, etc.)
3) Scale to 800x600