Might not still be useful for the OP; but for anyone else in search of some info.....
They do pair, and are mostly the same.
A few caveats;
Will need to run the same firmware (takes half an hour, once), on each speaker otherwise a few light shows won't sync (eg the equaliser doesn't exist pre firmware update).
The sync on the speakers is out slightly.
Noticeable on some patterns more than others, some being aided by the effect (waves), whilst others negatively do (equalisers colours being a small fraction of a second out of sync).
If one speaker has been 'used' for light shows more than the other, it's leds will prove duller.
Sadly with no brightness adjust inbuilt more creative solution might need be employed to equalise the brightness.
The app can prove a pain... a good thing is the pairing or party mode setting being 'remembered' allows pairing to one speaker and then pressing the connect button on both.
I often remove one of my speakers from my Bluetooth pairing with my phone - it will stop the jbl app from finding the speakers if two are connected (of the same type is my guess-I haven't tested with others), the rand as in I do this is to remove a delay 'handshaking' the setup that cans occur. It might be placebo but I feel the sync issue happens significantly less when only one speaker connects.
It is possibly a platform limitation of iOS or a bandwidth limitation if the connect Bluetooth method here used.
I notice when using android devices with Bluetooth speakers can shift the volume setting on speakers.
I use this as a trick to set the useful volume range of any given installation.
your mileage may vary (YMMV) but I encourage users to test this for themselves as I have owned many Bluetooth devices with differing ranges of volume they extract from the same speakers: between iOS and android, and shifting up on the android and switching back to iOS often yields much higher permanent volumes.
I set for undistorted sound as little compressed as possible, with useful steps in the volume dial.
They connect; but what I'm having trouble with is when I connect them, one always takes a while to start playing music. I think it may be because I have the charge 3 and flip 3 and since one is bigger it may take a while for them to connect, but I don't see that being why