How can I change system files to read/write for rooted Android 13 without TWRP?

I recently rooted my OnePlus Nord N30 5G using Magisk, but I still cannot edit the build.prop and hosts files (which was my reason for rooting in the first place). There is no TWRP in the directory for this phone. How can I grant myself read/write permission for these files without needing TWRP? This is my first time messing with the OS of an Android phone. I've tried following the instructions in this video: https://www.youtube.com/watch?v=5b_CMft4zlU , but I'm stuck on the very first step (after establishing the connection with adb), since I don't know where to find the systemrw file that he is talking about. Also, I don't trust the link in the description. I also tried to follow the instructions on https://droidwin.com/how-to-make-system-partition-read-write-on-android/ . On step 10, I do not know what this means, so I don't know how to decide what my "desired" partition size is. I just chose 1 and moved on. However, I am getting stuck around steps 14, as there is another prompt that the instructions don't warn about, creating another backup file. I selected "2" [Recovery/Row] and moved on anyway. From there, I was able to move on to step 19, but here I got stuck since I do not know what the "super.img" file that the article is talking about is, or where to find it.