Hi
@ckc. You can mix and match any type and form factor of Ruckus AP, as long as they all support the desired controller version you want to run, be it Unleashed, ZoneFlex or Smart Zone. Certain APs fall so far out of support that they just can't run with current models (for example, a first-gen Ruckus R7000 series alongside a brand new R850, etc.), but as long as you're on an R_10 or higher series AP, for now at least, they'll be able to co-exist with every model up to and including the R_50 series, on at least some version of the firmware. For Unleashed, it will typically be 200.8 and 200.9, to support the _10, _20 and _30 models all at once).
As for hardware spec, I tend to find the 700 series are actually
not the best fit for most residential setups, which usually call for APs with smaller/tighter broadcast spheres. The 730/720/710 are really meant to be sitting on the ceilings of amphitheaters, lecture halls, etc. -- places better suited for longer broadcast distance. Since you've got an R730, I would definitely test it versus one or two R510's. I suspect multiple R510's will perform better overall, but actually trying the hardware will let you know for sure.
Another thing to consider is power draw. The R720 and 730 require higher-power PoE (over 30W capability) in order to broadcast all radios at full strength and full spatial streams. The lower-power R500 and 600 series APs can all work at full power well within the confines of 802.3at PoE+, which means an easier time running all PoE from most access switches, without requiring either higher-power PoE injectors or 802.3bt switches.
All that considered, I'd probably err on the side of R5__ or R6__ series APs for your needs.
Let me know if I can help answer any other questions.