Custom build query

So I am about to build my second ever system. Been away from the scene for a year and a half due to personal life but want to come back with a storm. Heres the specs I have decided on at the moment and ill get to my query after.

Phanteks P400s Gun Metal Tempered Glass Mid Tower Case
MSI MPG Z390 GAMING PLUS Z390 LGA 1151 ATX Motherboard
i5 9600K 3.7GHz Six Core Processor
Cooler Master MasterLiquid ML120L RGB AIO CPU Cooler *
Kingston HyperX Fury Black 16GB (2x8GB) 2133MHz
MSI GeForce GTX 1060 GAMING X 3GB GDDR5 **
GIGABYTE B700H (700W) 80 PLUS Bronze Semi-Modular PSU
SSD and HDD but not worrying about them as of yet.

So I plan on overclocking the CPU so naturally I have decided to go with an AIO as I didn’t want full water cooling and the AIO really is minimal in the sense of size and looks great. But I am sitting at work and just reminiscing when I OC my i5 6600K from 3.5 to 4.6 with a be quiet air cooler and it was running insanely fine, keeping temps really low. So now do I get the AIO mentioned or get a really beefy air cooler?

My last build was a 960 frozr v oc 4gb, This GPU is only 3gb will that be sufficient for 4 months or so until I upgrade to the 20 series?