ok just seen some people on the forums a bit back saying they werent getting full gig over wired connection. should i need to set anything specific to achieve my isp rated speed or 1gig on the router, or just setup as basic and be ok to go?
The AC86U will do what you asked...
There are reports here of early AC86Us experiencing certain hardware failure. I have installed eight AC86Us; two early 2018 China builds from the same batch failed. Asus replaced one under warranty. I replaced the other. I am not aware of current AC86Us failing.
If you feel that Asus is willfully continuing to make and sell product with parts that fail prematurely, then you should not buy any Asus product, imo.
Not everyone wants to buy on the bleeding edge... your original post implied this as you wanted to replace an AC68U that has been on the market for a relatively very long time with an AC86U that has been on the market for a relatively long time. You did not ask about new WiFi6 product and even newer WiFi6e product that anyone considering a new router purchase would most likely consider, if they wanted to.
New product typically has a higher rate of hardware and software issues and costs a premium. Also, WiFi6* product is being introduced over an extended draft period of time. WiFi6 routers are being introduced and now some WiFi6e routers (with a 6.0 GHz third band) are starting to show up. WiFi6/6e client product introduction to the market will typically trail further behind and it will take even longer for users to take up to replace their existing WiFi clients.
The pandemic has further delayed the availability of routers (and everything)... supply is way down, demand is way up due to work and school from home network demands world-wide, and prices are way up.
The AC86U will do what you asked... without the typical new product and bleeding edge technology issues some prefer to avoid, and may be easier for you to source in your part of the world and will naturally cost less... all of which may suit your application, preferences, and particular needs.
It is not uncommon for members here to have a different take on matters. It is uncommon and in poor taste for one to disparage another over one brief, subjective, and well-intentioned post; or anything else. Instead, the mature members here simply post their point of view to help the discussion and learning along for everyone, subject to the time in their day.
My install notes may help you with commissioning your next router (no AX details yet).
OE