LaTEX for the formulas
My understanding is TeX is the typesetting language, while LaTeX is the language together with some predefined things, like it would be C plus the standard libraries. For formulas only, it is not needed to learn TeX. There are online helpers that can tell you the syntax, help you to find a certain symbol, and so on.
This post has a link with more examples than needed for formulas:
https://www.eevblog.com/forum/beginners/how-does-posting-math-notation-work/msg3994178/#msg3994178EEVblog forum supports MathJax, a LaTeX like syntax but not the full TeX language.
About Python vs a spreadsheet like Excel or Calc (Calc is the spreadsheet application from the free office package LibreOffice, compatible with Excel), or spreadsheet vs Matlab (Octave is the free Matlab, also compatible) use whatever comes natural to you.
A spreadsheet would be easier to draft some calculations for a one go, Python or Octave will be more powerful but will require more effort.
The spreadsheet wins for draft calculations, because you can see the result "live". You type the input number in a cell, hit enter, and in another cell you see the result instantly, all under your eyes and at known positions on the screen, easy to comment about them in a nearby cell, to color them, plot a chart with a couple of mouse clicks, to save all for later, and so on.
When it comes to more elaborated data analysis, then Python (or Octave) is the right tool.