As retailers prepare to report earnings, investors should gear up for a mixed bag, particularly for Advance Auto Parts Inc (NYSE:AAP) and BJ’s Wholesale Club Holdings Inc (NYSE:BJ). Walmart’s High Bar, Costco’s Layer Of PressureWhile Walmart Inc (NYSE:WMT) set a high bar with its recent performance, JPMorgan analyst Christopher Horvers believes Advanced Auto and BJ’s are unlikely to match it, especially as Costco Wholesale Corp (NYSE:COST) adds another layer of pressure. Costco recently announced a membership fee hike, raising its Gold Star membership fee by $5 to $65 and its Executive members…