Yes you can have more than one extender. It does require a little more work and playing around.
A true mesh system is needed if you want the simplest setup as then the main router is in control of how the router/satellites allows devices to roam and to switch between 2.4ghz and 5ghz. this would be an Orbi type system.
A lot depends on how you're setting up the ssids as well. If you're wanting to utilize the one name (single ssid) feature, then from my experience a star setup works best. If you try to daisy chain extenders, then the best results tend to come from when you give each extender its own ssid. Reason why it works best is sometimes the distal extender tries to connect to the router instead of connecting to the other extender.
daisy chain: Router---->ex75000---->ex7500
star: ex7500<----router----->ex7500
Again, a lot depends on playing around and seeing what works best for your setup. If you're running the single ssid feature and its connecting to the wrong access point, then turning that off and giving a name to the individual extender might help.
Therefore, the EX7500 isn't really a Mesh range extender; it's just an extender that allows for a single ssid. Shame, I bought it on the basis that it was a true Mesh extender. Oh well!
If you have the option to hardwire one of them, it'd work great. Problem when you start daisy chaining extenders is that your latency and potential errors increase.
As well as they are designed to function with 1 in a network. When you start buying multiple, you might as well as went with an orbi setup as you'll be hitting that price range. Then you get something designed to do what you're attempting.
