I made the switch earlier this year - it was actually pretty easy.
Before I pulled the trigger and bought my 1st Chrome OS device - I decided what I just HAD to have work in a Chromebook. One thing was a checkbook register program. I looked at several on my android phone, and finally found one I liked to replace Quicken. I tested on my phone first.
I now use Volkron Checkbook. I think I paid $2 to buy the full version. It is an Android program, but it works great on the Chromebook/Chromebox.
I also needed a Photoshop replacement. I tried several, including some that Leo has previously suggested. But, I found Pixlr Editor to be the best and closest to Photoshop.
That’s about it - search for whatever equivalent programs you need to have on the Chromebook. But, you WILL have to get used to not saving files on the computer. You use the cloud most of the time. You CAN save stuff to the device - but I only save apps and Chrome extensions on the internal SSD. You want to do this because if you need to do a powerwash, you will lose any files on the computer’s SD (hard drive).
If you don’t have any actual files on the device - IF you ever have a problem - just powerwash if need be. It will redo the OS, and you start up like you did when you first bought it. In the next 5-10 minutes, it will automatically download and install all the apps/extensions you had before. It does it automatically. In less than 10 min, everything will be done and you are good.
Now, I DO use the SD card as a small hard drive. I have a 128GB SD card in all 3 of my Chrome devices. I fill it with all my music, videos and lots of other files. THAT, you can use as a hard drive. And, if you powerwash the computer, it does not affect the files on the SD card.
Now, one tip - I keep my wallpaper and my profile icon saved on Google Drive. If you powerwash anything, you will have to redo the wallpaper and icon. So, it is helpful to have that on Google Drive, available for download if you need it.