The standard maple leaf is the 60 degree, but if you run low powered to increase the ROF say 310 fps and are never going to push the gun up to 345 you might try the 50 degree. It's softer and needs less pressure to get a good backspin. Regardless of the shore hardness of the bucking you need to use the correct nub for the bucking. If you go with the full maple leaf system then there is no need to flat hop or Rhop the gun.
It depends on how you use the gun as to the one you pick, If you regularly put 3000 rounds through the gun in a single day get the harder rubber, If you are more frugal and take single shots for kills and only use 500 rounds in an average skirmish the softer one might suit you more at the cost of increased wear.
The correct nub:
https://www.ak2m4.co.uk/internal-parts/hopups-rubbers/maple-leaf-nub
And the 50/60 degree bucking.
https://www.ak2m4.co.uk/internal-parts/hopups-rubbers/maple-leaf-macaron-50-aeg
https://www.ak2m4.co.uk/internal-parts/hopups-rubbers/maple-leaf-macaron-60-aeg
AK2M4 is away ATM, and he restocks very regularly, so what he doesn't have in stock this week will be in in a couple of weeks.
The ZCI barrel would be fine, Much better than a madbull or other budget tightbore. You need to measure the inner barrel length, I believe yours to be a 290mm, but taiwangun have it listed as 290 and GFC have it listed as 200mm. So measure it to be sure. If you go too long it'll stop your tracer unit working as the inner will be shielding the BB. So measure twice, and buy once.
Again AK2M4 will have something that will be close to what you need.
He's expecting a restock soon for the most common parts.
I wouldn't upgrade the hop unit unless it's giving you problems. AK hops are good units and generally run for a very long time before they develop faults.