You will get junk, period. No, you probably won't see those items in you recommendations, but considering you're already at 300 I can't say you won't at all. Even with just like 7 games in my recommendations, stuff will be added every now and then by amazon and some of the things aren't very related to gaming at all. Quick picks are not 100% dedicated to your recommendations list and then, as I quoted:
1: Some items can not show up at all.
2: Items showing in your recommendations simply based off of ratings, not purchases, have a very low chance to actually come up. I have a second amazon account with about 40 games in the recommendations, just to see if anythings pops up, and I've only seen a handful of games in my quick picks over like 2 months, whereas my main account(with pre-orders aplenty) get games in there constantly.
3: I'd narrow down your list anyway because I'm going to say that out of 300+ items, you aren't going to buy all of them just because they get a 5% price cut by being in your quick picks.
4: Refresh some ratings/pre-orders, something. Maintenance.
*Edit*
And dammnnnnn my quick picks are updating fast. 3 days ago 1 am, 2 days ago sometime between 6-11pm, yesterday between 3-6pm, and today at 12pm just now.
Got Crackdown 2, no last rebellion. WRONG! I forgot it doesn't have box art, I did get both in my quickpicks. Score!