Follow ups, oof. I still struggle with those in my day job but depending on what the pitch is would determine how I follow up.
If it's to send me a, "hey check out this web series I'm working on," maybe give me a week. I would also advise people not to follow up on Twitter. I keep my DM's open but I honestly was floored when a web series DM'd my personal Twitter asking if I've read their email, safe to say, I deleted it.
I think you've got a pretty good grasp on follow up protocol. If you know this person strictly covers web series, then I would follow up but maybe if you don't hear anything after the 3rd or 4th time, give them some space.
In my case, I am responsible for majority of the pieces you guys see. I have people like Nick Feldman and Aria Bauer who contribute as well, but more on a feature-piece basis. So it takes me quite a bit of time to respond to everyone. I literally have about 100 emails sitting in my inbox that taunt me every single day, but I take the time to personally reply to everyone and give my feedback. I think taking the time to get to know the person you're pitching too helps.
I know when I pitch journalists, I follow their Twitter accounts and when I'm pitching them something I think is right up their alley or literally something they're talking about it, but then find they're not replying to me, I take a look at what's going and sometimes you'll see they're traveling for a conference, or maybe they're on vacation. Stuff like that helps, then it gives you an opportunity to in your follow up to reference something.