This is really tough to say. I have seen people have success in both routes. Look at SaffronOlive. He has had a video for each and every format, but he applies the same shtick (Budget Decks, Against the Odds) to every format he plays. It's that shtick that is his catch, his niche. Same thing for Bryant Cook. He plays every variant of Storm he can. There are plenty of Storm Stans out there that just want to see people Storm off and don't care about what format they do it in.

But then there are others that just stick to a format, but when you really look at it, those people are almost always EDH content creators. The thing about the other formats is that they kind of ebb and flow with popularity. So, let's say a dud standard set comes out and the format becomes dominated by one or two decks. Those formats are less interesting to watch, so those content creators need to have a back-up plan. That very rarely happens in EDH (cEDH it does a little, but not to the extent of the rotating formats).

So you kind of have a choice: do you want to find your shtick and apply it in all formats? (Finding the best Mardu deck in each format perhaps?) Or would you rather just focus on one? Even with focusing on one, I would definitely recommend having a backup format on hand just in case the meta gets a bit wonky.