Hi Vagrant
Well, not sure about running at 60fps all the time, even in production you will see that if you have the blueprint editor open, this consume lot of RAM, (really a lot), OBS is your best option if your intention is capture with software with 1 single computer, I used to stick to .mkv with full quality, about the sound you will need buy some good headset, sound is very important! I have 1 corsair gaming void 7.1 and the sound recording is unfrikingbelivable, finally about Windows Movie Maker, totally not, use something more professional, at least after effects, you will see how flexible is for quality output
Anyway I do not make tutorials jaja, I just record stuff once in a while for my job
Cheers!