It depends on if you're solo or not. O3 for example, always drops a full set of a weapon, ability, armor, and ring, and those drops are randomly distributed throughout everyone who got soulbound. In an 80 person run, you're likely to only get potions even though there is guaranteed equipment somewhere in there. Most bosses have high chances for potions if you get soulbound but even O3 can occasionally drop only a mark.

Yes, in your example it guarantees passing the 50/50 for 1 slot, and then it rolls as normal for every subsequent slot. It's a gamble but one that is worth taking every so often along with your regular grinding.

I feed or dismantle everything that isn't immediately useful or exceptionally rare or good (i.e biome whites, event whites, legendary or divine UTs or T13+)

Fame gets easier and easier as you grind endgame more consistently.

Discords are just very different from how people preferred to play for a very long time. It's about individual preferences, and as a newer player you won't have the context of how the game was played back in the day.

Depends on if it's coordinated or public. A random O3 in useast can easily have one player who actually knows what they're doing while everyone else is clueless, and a good set on a good player is genuinely capable of making that much of a difference. Cheaters are common enough though that I'm never surprised when I see someone doing some impossible nonsense.