You might just jump to the Intel 8265.
I have a 7260 on an older system Inspiron 1545.
The DW1704 currently in the OP's system is an mPCIe card. The Intel 8265 is only available as an M.2/NGFF card. Even if there were some adapter board to make that work, the physically different shapes of mPCIe cards vs. M.2/NGFF cards could create fitment issues in that particular system. The Intel 7260 was the last Intel WiFi card available in mPCIe form factor.
I already recommended that card in your other thread. Hopefully you'll get an answer from someone with direct experience on your system if you really need that reassurance, but the 7260 costs $25 and is physically tiny, so even in the very unlikely event that it didn't work, it would be simple to return. The installation itself is very easy as well. Just make sure you uninstall the Dell WiFi software first, and also make sure you snap the antennas onto the new card securely, otherwise your signal strength will be terrible. I find it's easiest to connect the antennas before you install the card in the slot, since that allows you to get a finger on the underside of the card directly under the antenna connectors, which means you can sort of pinch the antenna onto the card.