I'm trading an arb player, but arb ends in the next cycle. Do I accept the trade as is and the AI will complete the salary or do I arbitrate first and then accept trade?

Talk to the owner who you are trading the player to, and see what he wants you to do. Either way, the trade will still go through.

^+1

I just did a sign and trade with arb going through before trade went through. I sent two arb players in deal to other owner. He wanted long term deal for whatever amount and years the player wanted before arb. One player wouldn't sign long term. The other player i signed for the new team for the two years that the player wanted. The deal went through even though one player was arb'd and one was signed while deal was waiting to go through. So, yes ask other owner what they might want to do.