I think it would be totally un-Snead-like for him to trade up for rounds 1 or 2. Whatever trades would be to trade down in order to acquire more top 100 picks.
And, I think that any possible trades will largely depend on what Snead/McVay seeing happening in the picks before they choose. If they have a couple of players circled that look like other other will fall to them, they'll stand pat. If it looks like they won't be there, but the next player on their list can be had a few picks down, they'll try to trade down.
But, trades require a trading partner. So, it's not like Snead/McVay can just decide to trade out of the spot.
It's a very fluid process, which is why Mock drafts are utterly useless.
