There is an old rule that you need at least 2 times the frequency that you wish to view.
There is a publication by the ARRL "Oscilloscopes for Radio Amateurs". On Amazon.com is near 20$ used or about 10$ for the kindle version that maybe helpful. The kindle version can be viewed via their free PC app.
Also there are videos on YouTube on choosing an oscilloscopes. I have a Hantek DSO5202P it was far more functionality then I need. I did have to replace the display after about three years but they are not expensive.
40 views and no advice?
The problem I have is that I answer so many questions that I like to give others a chance to answer some. But that is not always helpful I know.