If you fear the ISO that you download yourself, directly from Microsoft, then I can't help you.
The reset function in Windows 10 allows only 2 options: keeping one's user data files or keeping nothing.
I presume that most people want to keep their files and apps, thus the repair install. There is nothing safer than material sourced directly from Microsoft. It's up to you whether you want to proceed or not. But I have given an expert opinion as well as step-by-step instructions, and I won't be changing either.
Brian - Windows 10 Pro, 64-Bit, Version 1903, Build 18362
Many of the insights of the saint stem from his experience as a sinner.
~ Eric Hoffer