Feedback for my first build idea?

[Spencer97]

Budget (including currency): roughly $800.00 USD 

Country: USA

Games, programs or workloads that it will be used for: Regular zoom meetings, gaming, small productivity 

Other details (existing parts lists, whether any peripherals are needed, what you're upgrading from, when you're going to buy, what resolution and refresh rate you want to play at, etc): 

I already have a 600 watt Thermaltake 80+ Gold Power Supply.

Also already have 4x8 G 3200 MHz DDR4 Corsair Vengeance RAM. 
Used these to upgrade my current SFF refurbished office PC (HP Elitedesk 800 G2 with an i5 6500) 

Thinking of buying towel my build 

 

Case: Corsair 4000D Airflow

Motherboard: Prime B660 Plus D4 

CPU: i5 12600k 

RAM: 4x8 G 3200 DDR4 

CPU Cooler: Thermalright Peerless Assassin 120 (dual fan/ tower 6 heat pipes, comes with LGA 1700 socket I believe) 

Power Supply: 600 watt Thermaltake 80+ Gold

Extra Cooling: full allotment of 6x120 mm Case fans

Storage: 256 Gig SSD with Windows 10 Pro

plus 5 Tb external HDD Game drive 

GPU: (currently have but going to sell- RX 6400 Form factor version) thinking of upgrading to RX 580 (older but cheaper with decent reviews and performance from what I can tell) or RX 6600 or 6650 xt if worth it. Open to other options. 
 

I run a dual monitor setup both 1080p 

For gaming I like a lot of RPG, MMO games (RuneScape, SWTOR, Star Trek Online) as well as RTS like the Total War Series (Napoleon, Empire, Shogun 2, Rome and Warhammer), Ultimate General, and Turn-Based strategy/ Base Building Games.

Also enjoy games like Battlefront, Battlefield, State of Decay.  
 

Haven’t bought anything yet but been looking, researching and shopping, but I’d like to save more money if I can while also maybe potentially moving it to where it’ll be worth it. 
looking for feedback on what’s good, what to improve, for my first time plus any tips. Thanks a lot, In advance !!