I would expect a lot of congestion from traders moving their coins around. It will be worse for the BCH dumpers because there will be so few blocks, more then offsetting the 8 MB block size. But both chains will be congested for a while.
You are one of the first people i have seen that has mentioned this, it seems obvious but no one has addressed this. If you keep your coins in a wallet off an exchange (recommended method), you will have to quickly figure out how to split the coins/ spend on the new chain, along with everyone else that will be stuffing transactions down the network. Once you get to an exchange (confirmations are going to be interesting) its a race to the order book to sell the coins.
But if you leave them on an exchange that offers 1:1 (not recommended) you run the risk if not actually owning your coins, but skip all the traffic.
this is actually a difficult choice.
The Exchanges that accept BCH (/BCC) are listed here:
https://www.bitcoincash.orgFor example, Bittrex, has pleaded to making BCH available to anyone with BTC in their account (not on pending status). But when will that be available, or how, or even if they will setup a BCH/BTC pair (or any other) is unknown. Had I done more due dilligence I'd have chosen one of the exchanges committed to making the BCH/BTC trading pair immediately, and a pre-fork split (even if as tokens initially on the BCH branch).
If you use Bittrex, it's unknown when you'll be able to sell (90% of people) or buy (10% of people, wag) BCH, which means instead of selling 1 BCH = $280 it may be the case of 1 BCH = $0.28. However, I don't think Bitmain and ViaBTC want to do the most riddiculous move in the history of cryptocurrency, so I think they might have a mitigation plan.
If you are not on one of the exchanges that do 1:1 and enable BCH for immediate trading (even if on exchange only) then you may be late to the initial stampede sell, and it may be the case that holding it (waiting) may be best than duping for nothing.
Bitfinex and Kraken are the ones best knowns to support it for west world. But the deadline for entering the token sell is over (if you move BTC to Bitfinex now, you are late to the token exchange).