Will ALL activity and replies from ALL linked platforms show up under these tabs on ALL platforms?
Yes. Any activity on the Steem blockchain will be reflected on these platforms/frontends.
Like, now that I've actually joined D.Tube instead of just signing in with my Steemit account, I can collect DTC?
Not so much familiar with Dtube.. but I think you should be able to collect DTC either way.
Huh. Interesting... so... even if I never create a separate account on the various sites, I could collect any of the tons of random tokens?
Yes, you don't need to create different accounts. Like @acidyo said, all you need to do is use the tags to earn those tokens. For example: creativecoin, palnet, etc.
Thank you
For the steem-engine.com tokens you need to use specific tags for the posts to show up on their front-ends and be upvotable with their tokens, I recommend you use steempeak.com to be able to view the amount of upvotes you get in those specific tokens.
Ah okay, interesting. Thanks. So it's more about the tags than completely joining each individual site (like, i can join using my main Steem account and dont have to keep making separate ones)?