That's the issue right there. Samsung chips are faster, or rather people figured out the timings for those chips that result in higher hashrate than with Hynix and Elpida. This is what matters the most for Cryptonight.

This is just the starting difficulty, it doesn't matter all that much cause it'll auto-adjust to your hashing power pretty soon after the start. 7777 is the port to use for multi-gpu rigs. And 100k difficulty is for nicehash and similar services, you don't want to use that: it'll adjust automatically as well after a while, but you'll just lose some time not finding many shares (if any).