Well from my point of view. I would definitely go for CO2 as the foreground HC does need CO2 to grow well. And for the moss, using chiller for lower temperature will bring the moss out to the fullest.
For filter wise, it's up to individual as some people go for canister and some don't. Surface skimmer is not a must equipment but it does suck up all the surface dirt and prevent having a oily film on the surface.
For the plant on the bonsai, i would go for willow moss as it really gives a low feel but bear in mind, you need to shape out the tree scape.
What you see may be just a foreground and a tree with moss, but you wouldn't know what sort of hard work does it take for the scaper to achieve that.
Good luck and welcome to the dark arena.
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