we the traders should choose the pair which is more appropriate to the concept of trading that will be used , if love doing scalping should choose the pair which has most lowest trading spreads.
the broker can affects the result of our trading with certainly , for that reason its very dedicated decision to choose a broker and we have to choose it with cool mind.
if your broker always make sure good security first of all and take very short time when time to withdrawal then you have chosen already a best broker.
trading so many pair at the same time could be dangerous as a new Forex trader , its appropriate to trade in demo to see the performance how currency pair works.