Connectivity

If I understand correctly, 1). to use broadband, you need have a WiFi enabled router, then your can enable WiFi non your Note;  2). to use 3G data card (not the SIM card in your Note), you need a MiFi. Then your Note can connect to it through WiFi.  (of course, there are a few wireless routers can also insert 3G data card)

First, you cannot connect USB modem directly to Galaxy Note, although your Note has a micro USB port, because Android does not have drivers for these devices.

In the USB modem, there is a normal SIM card. Normally, you can put this SIM card in your Galaxy Note and get the same service as you put in the USB modem. But in some regions, some carrier may pose some limits  on using such SIM cards (which usually bundles more mobile data).  SO, you cna try to take out the SIM card from the USB modem and put it into your Note to see whether it works or not. (Galaxy Note can only take one SIM card, you need remove your original SIM card).

If the SIM card works in your Note, very likely it will also work in any wireless routers or MiFi with SIM card slot.  Then, you can conenct your Galaxy Note to MiFi or wireless router through WiFi, MiFi is small enough for your bag.

Anyway, whether it works or not depends on how the carrier limit the usage of the SIM card.  By default, inside the modem, it is just a normal SIM card.