Interesting question. Unfortunately, it can not be answered simply, so I will address it in parts.
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Hoarding vs. savings. Savings is the simple act of delaying consumption. This means that whether you store your money under a mattress, lend it out, or invest it directly, you are engaging in savings. So it is not a simple hoarding/saving dichotomy, they are just multiple manifestations of savings. A baker can put his bread in the cupboard for later eating, and that is just as much an act of saving as selling the bread and storing the cash, or loaning it to a friend.
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Hoarding vs. Investment. When you save, especially when you save in the form of cash, you have already done your productive work, and sold your resources. That means that whoever purchased them can use them however they will, including investment. Even if the baker puts his money under his bed, his bread has already been sold and can be used for further productive purposes. By delaying his consumption, there are more goods to go around for everyone else, lowering interest rates, and presumably prompting more investment. Just because you are hoarding does not mean that you are impeding investment.
Now that meanings of the terms are out of the way, I can try to answer your question.
Under the FRB system, there is initially more speculative activity than otherwise, because interest rates are artificially reduced. The inflation caused by FRB also stimulates investment, because otherwise people would be losing purchasing power over time. This increased rate of investment cannot last, however, because it is not backed by real savings. In the end, you get a boom/bust cycle, and malinvestment, as opposed to healthy economic growth.
However, if we were to switch to a 100% reserve system, investment would not necessarily decrease. Savings would be more attractive, because interest rates would be higher. Since there is no inflation, and no unbacked loans, real money has a better chance of competing. So bakers would be more likely to save, and less likely to spend their money, as it will be worth more in the future. But what about hoarding? Again, just because you are hoarding your cash, doesn’t mean that everyone else is hoarding your produce. Investment is done by entrepreneurs using real wealth, not cash. Investment can continue, and may even increase under a 100% reserve system, because the actual amount of saved wealth will be higher.
It is hard to say exactly what the results will be, but I can only presume that the current incentives against savings (namely, artificially low interest rates and inflation) would be reduced in a 100% system, and that investment would increase if such a system were to be used. This is not necessarily true, however, and the direction of the market is difficult to predict.
Will people buy more or fewer cars under a 100% reserve system? More or fewer houses? Very similar questions, but just as hard to answer.