help achieving actual isp download speeds (wifi)

For the AC 9260, it is a dual band adapter that supports 160MHz channel width on that band, this makes for a PHY rate of 1733Mbps, and usually a real world throughput of around 900Mbps

This article shows the 160MHz performance with your WiFi adapter.  https://www.smallnetbuilder.com/wireless/wireless-features/33212-160-mhz-wi-fi-channels-revisited?start=0

For your motherboard, instead of using an m.2 WiFi adapter, they instead use the a smaller 1216 style form factor that is soldered directly to the board, thus they cannot be replaced, so an upgrade on the desktop, would essentially have you using one of the m.2 slots, though in that case, for best performance, you would essentially be using either a PCIe to m.2 adapter, for example, https://www.amazon.com/Desktop-Wireless-Network-Converter-Including/dp/B01MFGYAX6/

Though at that point, it would be cheaper to just run some Cat 6 between the router and your PC.

Another option on a desktop is using the chipset connected m.2 slot (one near the bottom of the board), and a u.fl to rp-sma connector adapter to attach some antennas to an expansion slot opening on the case. Furthermore, the AC 9260 wil have to be disabled in the BIOS/ UEFI settings for the motherboard). Save the top m.2 slot for your NVMe SSD since that connects directly to the CPU and does not share bandwidth with anything else, while the chipset lanes share 8GB/s worth of throughput with everything on the chipset.

While there is no noticeable slowdown in the vast majority of cases, it is possible to notice a slowdown on an NVMe SSD on the chipset m.2 slot if while reading from the m.2 SSD, you are also accessing a number of SATA SSDs, in addition to also accessing one of the 10 gigabit USB ports with high throughput components all at the same time.

Beyond that, if using even 802.11ax,when using a 160MHz channel on the 5GHz band, part of the signal will extend into the DFS frequency range, which by law requires transmit power to be limited to 250mw transmit power. While in many cases it will not be an issue, if you are far from the access point, it could result in there not being much of any performance boost, or worse, if in a congested environment, slightly slower speeds than on the 80MHz channel width, thus it is something to experiment with. Basically if you are multiple rooms away from the router, then you test both 80MHz channel width, as well as 160MHz channel width to see which offers the best performance (it is pretty rare to get a performance drop on 160MHz).