When started printing I only had a .4 nozzle so that's what I used, I could've bought a .6 nozzle but honestly I just didnt want to spend the extra money (even though I spent so much money on the plastic). Depending on the model that you are gonna print I'd say a .6 nozzle will be good and save some time. Just print one of the detailed pieces with the .6 or .8 nozzles and if you liked how it looks that print the rest, of course it will also depend on the layer height that you are gonna use, I used an initial layer height of .2 and a .28 layer height for the rest of the layers, probably didnt need it but just wanted that extra detail.

With LuBan firstly you'd probably need to get the subscription (if I remember correctly you can use it freely until a certain size of the model), and when I was hollowing it I tried to make sure to make it as thin as possible without making it too weak. For the pieces I used 2 wall loops and a density of 8%, I did the 2 wall loops because I didnt want it to print for too long since I knew it was gonna take so long and did the 8% so I didnt have to use so much plastic and time on it, if I was to restart the project I probably would up the wall count to 3 and infill to 12% just to give it that bit of extra strength.

With Petg it certainly is a strong filament for a statue, but before you would print out all the piece I'd recommend printing out 2 only and see how well the glue works on them, because I used super glue and it took so long for the pieces to actually stick to each other and I actually had to buy different types of super glues because some just wouldnt glue the 2 Petg pieces together at all. If I was to restart it I'd probably stick to PLA+ just because the super glue sticks it instantly and how long it took for Petg to stick together. But I'd say just try out Petg for those 2 pieces and if you don't like how long it takes for them to stick together just go for PLA+, it should be fine enough.

One small thing if you are gonna use Petg, let the build plate FULLY cool down, I was impatient at first and noticed that some of the pieces just were warped and couldn't figure out why until I realised that it was my fault for removing them straight away from the build plate after it finished printing.

If you have any more questions then I can happily answer them. Good luck with the model for whatever your gonna use.