Was on Taveuni a few yrs ago. There no liveaboards leaving from there at that time and not familiar with any working their reefs. All diving was on Rainbow Reef from land based locations. The closest to the reef was Garden Island Resort (GIR) but I did not stay there...stayed at Maravu, which is mostly honeymooners and no divers. GIR is a former Super 8 style bldg and you can see that immediately from the structure. GIR is not close to anything else so its a cab ride to anyplace else. rainbow reef diving was nice with large tidal currents. Local guides follow the tides so you always are diving on the leeward side and had little current during the dive. Safety stops are from a reef hook/rope and you blow in the breeze of the current for the 3 minutes.
Many others had reviews of GIR and seemed to like it overall. They have a gravel/rock shore line but a nice view. GIR was a divers spot so its culture was more dive oriented compared to our honeymoon culture.
Maravu was high priced but picked it for making the wife happy while I was off diving and she liked it a lot. The Matei point area has several places to eat and stay. We liked that area a lot and would stay there again if we visited again but I might pick Coconut grove for the lower price.
The dive shop I used closed the next yr.
All diving, last I knew, was on ~24 ft open boats which are quite windy for commuting. A wind breaker designed for salt water would be quite useful...I loved having mine.
The waterfalls are worth the trip.
There is a pizza place near Matei pointe that had great food and great views. I watched them cut the newly caught fish to make curry for me.
The slightly longer commute to the reef was worth staying in the Matei point area for me and would do it again. Trip advisor has reports on places there along with one from me on Maravu from that time.
Sorry I cannot be more specific in answering your questions but things have changed since I was there.