First of all you have to separate the two RCM sections, i.e. RCM u/s 9(3) and RCM u/s 9(4).
RCM u/s 9(4) is for unregistered purchase and is no more applicable, irrespective of any limit. Old section has been abolished and has been replaced with a new one, where it is applicable to notified persons and goods, but that’s a separate issue.
Now, RCM u/s 9(3) relates to freight. But it will be applicable if the transporter is a GTA, i.e. Goods Transport Agency, whether registered or unregistered.
But, if the transporter is not a GTA, means does not issue any consignment note or lorry receipt like unorganized sector or individual truck owners, then GST is exempt for both in and outside state.
Further, if the transporter is a GTA but the consideration charged for the transportation of goods in a single carriage does not exceed INR. 1500 and for all goods for a single consignee does not exceed INR. 750, then also GST is exempt.
So, in case of freight, you have to decide accordingly.