I think 4 accounts is needed. As Facebook policy is quite strict, there is a lot of tiny things that may lead to your account locked/flagged. So when 1 account is locked, 3 other accounts for 3 stores still running. If you use 1 account only, all the store marketing will stop. It's about safety
Also, 1 pixel for 4 stores so cookies will be mixed together, you alway have to define it by URL, quite inconvinent
I've through the same just recently, I talked to both Shopify and Facebook customer support's and they both agree that in order to track different websites, it would be much easier to create different Facebook Pixels.
To create the Pixels:
- Create a Facebook Pixel in Business Manager
When the Pixels are created, you will need to connect them to the right Ad account in order to use them. Refer to the steps below if you need guidance to do so:
1. Go to Business settings.
2. Click Data sources, and then Pixels.
3. Give yourself permissions in the Pixels, through the Add People button.
4. On this same page, you can add the right Ad account with the Add Assets button.
5. Make sure to do steps 3 and 4 for each Pixel.
Personally, for each store we create a new account along with a new business account with a new Pixel.
This way its easy to follow and no confusion.
I didn't create a new Facebook account for each storefront, I just created different pixels in the same Facebook Business account, I've been working with this set up for some time now and it's working very well, it's good to have the different pixel information not mixed up, and is also easy to manage the ads for the different stores, sometimes I duplicate, create very similar campaigns, so having them all in the same Business Account is being very helpful.
@Tim15 It can be wise to setup multiple pixels per store, for the same ad account. Best way to do this is through some FB pixel app in Shopify. This gives you redundancy in case one pixel gets banned. Your pixel is your storage for who is visiting the website and who is likely to buy from you. It is gold.