General store vs Niche store vs One product store

Hey, I'm currently trying to start dropshipping but I'm having this huge debate with myself trying to decide which store to start, General store vs Niche store vs One product store.

I feel like if I do a one product store it would make the most sense as I would be doing a facebook advertisement for 1 product, but after I read a little bit about dropshipping by some successful people most of them recommended general stores. I'm really confused on why this is a good idea. Why would I have a store selling stuff that has nothing related to each other?

I don't mean to be rude but please only reply if you have experience with this.

Do NOT do a general store. At least not one that branches into 100 different categories. Either base your stores product on 1 niche target audience, or base your store on 1 niche target product(s). You'll go crazy marketing across different niches across different product categories - especially when you have not had prior experience. 1 product store is not suggested either. Its too limited, unless its a unique product that has a very vocal user group.

I've done a ton of research and everything I've read says what the above person says.

Yes, the best is to focus on niche store. There you have varieties of products in the subniches.

You can focus on one, most profitable product and add similar products from same niche. When you have more products your shop is also more trustfull. What kind of product it is ?