Nice looking setup mate
I like the rockwork!
The best thing to do when deciding on corals is choose the dominating major group of corals you want
SPS, LPS or softies or a mixed reef with a bit of each! Once you have that, you can gear the tank and fish towards those selections (or gear your tank towards your fish and then choose your corals haha) and do it that way
Always the easiest as so many corals are so beautiful
If you want a good climbing/covering coral to make those tonga branches look awesome, here are a few of my suggestions:
- Clove polyps as you've said
- Star polyps, they grow like wildfire and will cover it in no time but you'll need to keep an eye out so they don't tank over!
- Zoa's, so many colours and great little corals! Some of my favourites
- Morph's will also do really well in this type of situation, hardy and can be very bright and colourful!
It's all about what you want to do
I would stay away from xenia though as it grows like a weed and will take over before you even realise
Ask away if you have any coral questions and I'll do my best, corals are my favourite animals and I do try to know everything about them I can
So hopefully I can answer any questions you may have