First, separate the actions of taking notes versus reviewing notes versus storing notes versus processing notes. You may want three different classes of applications, one class to take notes, one to store them, and one to review/process them. Alternatively, the latter two classes of actions (store and review/process) can often be combined into one application, and the first action to take notes can be left to a dedicated "note taking" application that performs according to the need to allow fast yet coherent input.
Any options on taking text notes must be future proof. You will not want to struggle later to find a way to open content that you stored in an application that is no longer supported. The extreme extrapolation of this restriction typically means storing as vanilla ASCII text (although UNICODE will not go away in anyone's foreseeable lifetime). Markdown is an option to flavor the text when viewing it, while rtf is acceptable but can be cumbersome. Finally, LaTeX is designed as a tool to take text to printing, and the overhead when taking notes can be overkill. Markdown allows LaTeX, and this compromise can be leveraged nicely to allow you to type rapidly when you want just text input yet polish up later with LaTeX math when you want to see equations in a structured way for reading/reviewing modes. Be aware that markdown has various dialects, and one flavor of markdown may not translate to another.
The options to take notes also must not distort the original content. For images, this guideline argues to prefer PNG or PDF format to JPEG.
How you choose after considering the above is a matter of personal preference. As you explore, set a goal to have a workflow with the lowest friction. As one recommendation, don't fall for the one-app-to-rule-them-all guideline just because using more than one app gives added "friction". By example, I've not known a case where a multi-use app does as well as at allowing easy, intuitive note taking compared to a dedicated app for note taking. Also, whether you need to factor in using a multi-platform approach (iPadOS, iPhoneOS, Windows, macOS) can define or limit your options for applications.
What do you all think [about using markdown]? Is there a better way to approach this? Any tips or suggestions would be greatly appreciated!
I think you have settled on a reasonable and future-proof way to take and store typed text notes based on your needs. What remains is to choose applications for capturing images, coding, programming, or other equivalent actions. Finally, you may want to take some time to test various applications that allow you to assemble and process your collections of documents and notes. Applications in this category include Notion, OneNote, Obsidian, DevonThink, Roam, Typora, and others.
Best platform to keep ... notes?
My best applications for note taking and processing are tied to my two computer platforms (macOS and iPadOS). They meet two criteria: intuitive to use and effective to apply for the demand (take notes or process notes). The first criteria is a user-interface demand and the second is a workflow demand. I reached my choices on best applications to take or process notes through a process of elimination. When I find that an application is aesthetically cumbersome (ugly) to appreciate, or when I find that the application requires more steps to complete a given task compared to other applications, I eventually stop using that application.
In short, rather than asking in hopes that others will tell you what the best platform / application is, invert this question. What are your criteria to define best note taking and best note processing? Using those criteria and your limitations to the computer platform you use (Windows, macOS, iPadOS ...), test various applications. Finally, appreciate that the answer can (and likely will) change over time. Your platforms and applications will evolve, and your appreciation of what defines best for you will evolve.
All this being said, regardless of specific platform and applications, I hope my posting gives you an appreciation of how to approach the choices that you face in the best overall ways possible to meet your needs. When you want to explore more about this topic, search through the wealth of postings about it on general discussion forums things as outliner software (dot com) or (mac) power users (dot com) as well as on the blog/forum groups for the specific applications that interest you (e.g. obsidian dot md).