hey, not really a tech-savvy person but I wanted to know what USB modem is the best for my sft1200 opal, the only results I liked were the mifi, tp-link ac600 and some generic dev board with a sim slot, if anyone can drop me a suggestion or help me find a good and fast modem I will be very greatful

You mentioned the dev-board, probably can try GL 5G dev-board with 5G modem, and other USB-mini PCIe board with the Quectel EC25/20 series modem.

I recommend GL-M2 5G Development Board - GL.iNet