I don't find having a natural planted tank limiting at all, I've been able to grow almost every plant I have tried, the only ones that haven't worked are UG, HC, Limnophila sp. Vietnam and mermaid weed. I can grow glosso, Japanese hair grass, blyxa pretty much anything
I would go for the 6 tube one but that’s just me, I have the 8 tube. Keep in mind with a NPT you can have DIY CO2 if you want.
What about bundles of bamboo instead of terracotta? Looks more natural IMO.
Broad leaf chainsword are dead easy plants to grow, I almost had the chainsword take over lol so I gave heaps away.
In a NPT you want the plants to filter more than bacteria, sponges on the intakes are usually to prevent fry or shrimp being sucked up.
I love rummynose tetras, they look great in a planted tank schooling around. A pair of dwarf cichlids would also be nice, they got along well with my bettas