1. GST won't be applicable on the freight charges paid by you against the hired trucks.
2. If your client is registered under GST, you do not need to collect 5%... the client is supposed to pay the same under RCM. However, if your client is an individual or a proprietor & un-registered / not having GSTIN, you need to charge 5% GST on your Bills and collect the same from your client and pay it to Govt./treasury.