Yes, you should plan to go the GRR route. I honestly don't know if the walkway thru Bug's Land is open or not, we didn't even try to get over there before 10. It's definitely the longer route even if it is completely open to walk through. But even if you could- the cut off points for the Paradise Pier area is going to hold everyone in the relatively same spot- it's just 50 feet of separation between the two directions. The shortest route will be to line up at the rope one the bridge heading towards Ariel's Grotto (we went the other way, and I saw the folks beating us to TSMM from that route)
It's hard to say exactly what the routing will be like, as of August first Burrbank ICe Cream/the Bakery/Engine Ears toys get closed down and start to get removed, so expect more new construction walls in that area. They may direct all rope droppers only to the one side but for sure you should be able to get thru to condor flats and then up around to GRR. It's going to dump you off by the rope drop spots either way you choose to go.
I hope someone else can definitively chime in about the WOC/GRR fast pass issue. In April they did NOT have GRR FP up and running until after WOC fast passes were gone. However, others have reported the they had a couple GRR working and WOC FPs working at the same time. We didn't try in June, so I don't know how it's been going for the summer. Worse case, if you get in, on your way to rope drop, stop at GRR and ask the CMs how it may be working that day.