thank you alzhao,
I have a few more questions if you have the time and can answer them.

  1. I noticed the uboot had both types of flash to upload for nor and nand.
    I hove no problem doing a nor flash with an extroot for more storage space. so can I use the internal microsd for extroot?

  2. after testing it out if it isnt what i was hoping for do I flash the gl-stock.bin file to nor or nand? I was reading that it actually boots off nor and switches to nand but the interface says to flash .bin file to nor.

  3. do you have a link for the vanilla openwrt for 750s. (hoping its a higher kernel than 4.9
    issues is probably a kernerl problem or I jjust missing some .ipk in the stock gl-inet firmware… or maybe just a plain openwrt bug?

thanks!