Should I stop accepting/sending bitcoins in days before / after forking, or wait some more confirmations more than 3-6 ?
If you only care about BTC, it shouldn't matter. There is supposed to be replay protection for Bitcoin Gold, but even if there isn't, you only risk losing Bitcoin Gold by transacting normally with BTC.
The real risk in these forks (if they have no replay protection) is in trying to send the forked coins. Many users will likely get those transactions "replayed" on the original chain, and if the funds are sent to an address they don't control, they will be lost.
I hope that in the future we have more simplistic coin splitting tools to make it easy for users to dump their altcoins without putting their BTC at risk. At least, I hope to see RBF and nLocktime become more intuitive for users, so they don't have to depend on exchanges/third party services to split coins for them.
This is great news. So according to you I can safely receive payments on the bitcoin legacy chain (BTC) without risking a loss of my own bitcoin gold? But as you've mentioned the person who would be sending me a payment would be at risk right?
I hope that in the future splitting will become much safer. That way a lot of forked coins will get flushed out really quickly because a lot of big bitcoin holders are fearful for their bitcoin.