I can speak only as a consumer:
1) Nicely painted models.
2) Nicely painted scenery.
3) A scenic backdrop to the table is nice, but not necessary.
4) Any good video editing software should work, the only stuff I've worked with in the past was Sony Vegas maybe 5 years back. Good software. I don't know what's popular now.
5) If you're doing full battle reports they should be between 45 mins to 2:30. Cut out stuff people don't need to see if it doesn't affect the story you're telling.
6) The biggest part, and the hardest: charisma.
I watch quite a few battle reports, and 90% of them I stop about ten minutes in because the presenters are grating or super awkward to watch. There are a handful of YouTube channels which get this right and it's not something you can really teach. If you look at my favourite channel for 40K video reports, Tabletop Tactics, they're great to watch because of the interplay between the members. They're fun, light hearted and entertaining, while putting on a good show. That's the X-factor I'd say which makes/breaks a successful channel.
Look at other non-battle report channels and you see the same thing; if you're easy to watch, you're easy to watch. Uncle Atom from Tabletop Minions is a good example. Does a podcast-esque show on his YouTube channel where he just talks into the camera about stuff and responds to chat messages. He's charismatic, has a good voice and is easy to watch. That's rare.
Sadly charisma or stage presence isn't something you can really teach/learn, and it will appeal to people in different fashions. That's the only major hurdle I think for a lot of channels. Also if you'll be appearing on camera - dress appropriately. Some channels you see people who look like they just rolled out of bed and didn't shave or shower....if you're presenting a product (your YouTube channel), personal hygiene is still important!

Good luck! Do post back if you start some videos. I also think it's safe to say the first dozen or more will be awkward and weird and probably not get many views...it happens.