My ISP is offering the same price for a 1gbps and 3gbps
Would the following work?
- AXE16000 which has 2 10GBPS WAN/LAN ports - can I use 1 as WAN and another as LAN for PC
Check the official specs/manual before asking - yes - you can.
- For PC, I need to get a 10GBPS network card?
Not necessarily. There are many cheaper 2,5-5 Gbps cards in x1 SFF PCIe. But performance vary.
- Currently, I split my connection from ONT to Switch to 2 routers ( both asus ) but they are gigabit only, so I need to get a 10gbs swtich?
AFAIK, if your ISP provides 2 WAN IP's from ONT device - you can. With newest firmware and VLAN's I can think, that you can use
without a router cheap solution, where 1 router's (call it "upstream") 10 Gbps additional port is "sacrificed" do make mutual WAN domain.
But in your case - original 2,5 Gbps "WAN" port can physically handle 3 Gpbs ONT in the same config. But be aware - this router doesn't handle "bells & whistles" with AV, routing and etc. well on the WLAN / WiFi interfaces, above like ~350 Mbps. CPU is too limited.
Ethernet cable - YES.
Is this the right way to go?
Depends on what you are trying to achieve

. I have 1 Gbps 5G connection now, topping at ~950 Mbps and it is enough for me, as I do not game and have configured QoS so that VideoChat and VOIP(Voice over WiFi) has priority - they do no stutter even if download is consuming the rest of the throughput.
Always test:
1. "bare" connection from ISP.
2. Ethernet cable.
3. WiFi.
And do it with:
A.
WaveForm BB test.
or
B.
LibreQoS BB test
And read and understand and estimate this -
BB before.
if you would want to use your internet connection as a human, not as a data hoarder. From my perspective 10 Gbps switch without adequate
internal loads, like home data/media server/etc with RAM caching/SSD with NVMe is a waste of money. 2,5 Gbps wire-speed setup is more than enough and the lower the wire speed, the more cheap cable can be used, if distances from routers are short. You do not need 6A category, maybe even 6 and can go cat 5E for short links (like up tp 10-25 meters).
Have a nice day!
