Indeed it seems that
OBS (Open Broadcaster Software) is a popular choice for making recordings. For for recording the voice-over
Audacity probably is a good choice.
I am not really sure about what video editing software to recommend, but if you are familiar with the user interface of Blender, it actually have an at least somewhat decent video editor built in.
Regarding the audio, you can do a lot to improve the dialog audio and audio overall, like using reasonable recording levels, slight compression, dampening a few frequencies with the equalizer and loudness normalization (usually in that order). Today normalization is more aimed at getting the average level to a certain level rather than just the peaks. [1] A good free plugin to measure this is the
Youlean Loudness Meter. it seems YouTube is normalizing to -14 LUFS. [1]
You can do a lot with a cheap lavalier microphone and free software and plugins. Pareto's principle apply here (20% of the effort makes 80% of the results, you just need to know where to put the effort), and for audio equipment there is a steep diminishing return of investment. Past the threshold of reasonably good equipment most people will not notice the difference in audio quality if the price tag get another digit.
For the principles I can recommend looking around at YouTube videos by for example
Alex Knickerbocker,
Curtis Judd and
Rodolfo Piedras (RLFO Sound). Some good ones being
How To Get Better Dialog - Three Tools (14 min),
How to set up lavalier microphones / Rycote + Ursa tape +Topstick and more (14 minutes, though most of it is not really relevant here).
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[1] Mastering audio for Soundcloud, iTunes, Spotify, Amazon Music and Youtube, Mastering The Mix, May 26, 2020Edit: Added some missing words.