DIY Home Server

[SupposedlyAnEngineer]

Budget (including currency): 100k-150k PHP ($2000 - $3000 US)

Country: Philippines

Games, programs or workloads that it will be used for:
For Gaming: All games that can be thrown at the rig with maxed out settings(Fixed 1440p, Not aiming for 4k), Work Related Application: ITSM(BMC Remedy), RPA Solution, AD w/ Exchange/o365 (All On-Premise; Personal Dev Environment to be exact).

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): 

Existing Parts were r9 5900x, ASUS TUF 3080(pre-ordered(provided down payment for card reservation)/to be picked but I might wait for the Ti variant).

Now, the question is will there be a significant/huge impact on performance when I selected a b550 from x570?
I will not be overclocking the CPU for longevity and integrity of the hardware.

As for the memory I will stick with 3600Mhz RAM speed but I was conflicted with either go for full 128gb capacity of the board or 64gb only.

I can go for 64gb kit as it is always available here but the RAM might be insufficient due to the fact that the ITSM solution is the one that eats the whole memory of the system (Proper POC of the ITSM will go around 54gb of memory(DB included). I can resize it but experiencing the actual size for the Prod is the much preferred approach for testing as I have RPA to simulate the actual day-to-day load).
I can also go for 128gb but it is only available outside of the country and the shipment tax is 36% - 50% of the actual value of the item/s bought outside. (I might hold out on this as my previous co-worker will be flying to Poland and I can ask a favor to look for 128gb (32x4 kit) there. The down side is He's flying there next year January and not sure if it is 2 weeks only or 2 months).

For cooling, I'm also conflicted on going Full Air or AIO (cause to be honest, there's little to no impact on the performance unless you overclock it and go full LN2).

For Chassis, I planning to go with Silverstone GD09 for its Air Cooling Design, Orientation and can be place to rack mount.

For Storage, I'll go with Samsung Evo 970 (plus/pro) and expand the storage later.

For PSU, any legit 850w gold rated. I selected the 850w for more head room incase the rig eats more power (especially I'm running at least 6-7 VMs one at a time).

For Monitor and keyboard, I will think about it later as I can use my current LED tv and wireless KB/M.

Please provide your thoughts/constructive criticism in-case I missed/done something wrong with my target build and happy holidays to all of you.

EDIT: Sorry for the bad English!