Assuming you mean players eligible for the Kiwis - RTS, Taulagi, Mariner, Luai, Papalii, Nanai, CHT would all very much be in the running to make the Kiwis 17 this weekend, and I'm being a bit conservative there and saying that Paulo, Sua, Sasagi wouldn't (but not too far off).
From Tonga - AFB, I Katoa are the obvious ones that would walk into the team. Halasima and Toia almost certainly. Fotuaika, Finefeuiaki, Utoikamanu, Taumalolo, Vaimauga, Wong other possibles.
(b) is pretty obvious and the question feels disingenuous. Rugby league in New Zealand is played by a large % of people who qualify for a Polynesian nation. Certainly in Auckland, where I have the most direct personal experience, it is quite obvious that the game is dominated by Polynesians. I haven't crunched the numbers, but I would suggest that if you assessed all of the NZ-eligible players in the NRL, again, over 50% would be Polynesian.
At the international level, it's pretty obvious that the ethnic backgrounds of those representing the Kiwis is unlikely to reflect the ethnic backgrounds of those eligible for the Kiwis, or those who actually play rugby league in NZ, if NZ-eligible Polynesians opt against playing for the Kiwis in large numbers.
I find it encouraging that there are a good number of Kiwis of Samoan descent in the current side, for a while there it felt like we were turning into the NZ Maori/Pakehas. It's a bit farcical for me to go watch Auckland club footy on a Saturday which is 80% Tongan/Samoan, then watch a Kiwis team where most of that demographic have made themselves unavailable.