You can try them inside the case, but they're unlikely to have very good signal since they'll be inside essentially a Faraday cage.
I'd just grab a set of leads and antennas and swap them out for desktop antennas.
https://www.amazon.com/2-4GHz-RP-SMA-Antenna-Pigtail-Cable/dp/B07P8CKGZM/
Something like this or similar should work.
It's not difficult but it's fiddly, those things are tiny.
The Intel 9260 is the one to get imo, it has Bluetooth 5, while most other cards will have Bluetooth 4. Dont get the 9560, it's essentially the same card as the 9260, but it's only compatible with certain 8th and 9th gen Intel CPU's and motherboards. As for the antenna, I found this
I found it by searching "wifi antenna ngff" on Amazon.
https://www.amazon.com.au/2-4GHz-RP-SMA-Antenna-Pigtail-Cable/dp/B07P8CKGZM/
Antennas and correct pigtails. They ship from Amazon US, but from Amazon, as I didn't see any that were in Australia, but it may be because I'm in the US, it's steering me some. If that poses issues I'll try and find a different one.
Also, the case is amazing! Have my NUC8i7BEH in one. No more 90C+ temps just with little spikes in load, or even just booting windows. It's the best.
Ah, well that's why you're not getting any signal.
These will work https://www.amazon.com/2-4GHz-RP-SMA-Antenna-Pigtail-Cable/dp/B07P8CKGZM
Jm sitting here looking at them on Amazon . However it has a single mode and dual layer mode does it make a difference if i buy these?one has 2.4 and 5ghz with 6db and one is 2.4 ghz i think ?
2 x 6dBi 2.4GHz 5GHz Dual Band WiFi RP-SMA Male Antenna+2 x 35CM RP-SMA IPEX MHF4 Pigtail Cable for M.2 NGFF WiFi WLAN Card https://www.amazon.com/dp/B07P8CKGZM/ref=cm_sw_r_cp_apa_i_e5oUCbC4QEK4E
Eightwood 2.4GHz 5dBi WiFi Antenna RP-TNC Male Plug Omni-Directional for Wireless Router WLAN PCI Card https://www.amazon.com/dp/B010DE02Q4/ref=cm_sw_r_cp_apa_i_D4oUCbPX4NY3D
2 x 6dBi 2.4GHz 5GHz Dual Band... https://www.amazon.com/dp/B07P8CKGZM?ref=ppx_pop_mob_ap_share
These will fit the WiFi card and have great reception, and you can lose the Asus antenna. Great looking build BTW!