Thanks for all the feedback.
i had bough RT-AC86U last weekend from hikari85 and mesh with older RT-AC68U.
on last weekend also TM came and upgrade my measly 8mbps streamyx to Unifi 300mbps.

with 5Ghz; able to hit 250-310mbps; while with 2.4Ghz, <100mbps.

have a question(s) regarding Asus AiMesh.

[attachmentid=10419369]

setup 1
from above pic (left pic); in orange box
1. the setting based on AiMesh with wifi. RT-AC68U placed on 2nd Floor. Z-height distance from 1st floor around 3.2m; while X-axis distance round 5m. the speed drop to range of 110-170mbps with 5ghz.
2. is normal for AiMesh to drop is such away?
3. in my in-law house, which using Unifi 30mbps; i setup their router with powerline (aztech AV500) to connect between 1st floor and 2nd floor router, the speed in both floor condition hovering between 24-28mbps.
4. is related the higher the speed, the bigger discrepancy it will be?

setup 2
referring red box
1. i setup using TP-LInk AV1300 homeplug AV2 to connect between RT-AC68U and RT-AC86U. during initial pairing for this setup, im using ethernet cable to setup the AiMesh between these 2 routers.
2. the speedtest shows (with 5ghz); just between 70-80mbps. not able to get pass 80mbps at all.
3. in my previous setup (prior to unifi with streamyx 8mbps); connecting RT-AC68U (1st floor) ---> Powerline AV500----> Powerline AV500 --->Dlink router (2nd floor); still able to maintain 7-8mbps which was comparable to 1st floor speed.

anyone can shed some light as i thought with AiMesh; both can produce smaller difference between these 2 routers in regards to speed.

Thanks in advance.