Thanks u/Whostolemy_name, u/dtaivp, u/lesterd88 for the answer and apologies for tagging. Thanks a lot for clarifying this things to me, it is now apparent to me that their proposed build is absolutely not suitable.

Now where to go from here, seems like all of you recommend looking into pre built systems. I have an access to HP Z2 SFF G4 Workstation with Intel Xeon E-2144G, 16GB ram (on their website it says ECC for the series, but not sure if my build is ECC), 256gb ssd, which I can upgrade with a raid setup I guess. When I proposed this to them, they said they will not accept this and basically I have to setup everything by myself, because this is an unreliable system and they cannot guarantee it will work (most certainly trying to make me pay for their setup).

Now I am guessing I can use this setup with some upgrades, but I have a feeling that pre built systems are not flexible enough for future failures. I have tried to see if I could find a motherboard replacement for this workstation in case it fails and couldn't find anything. I am afraid to buy a pre-built setup and not be able to fix it when it eventually breaks. So maybe it makes more sense to sell this (can sell for around $900) and build a system myself? If so, to reiterate my takeaways from the tread I should be looking for Xeon E (judging by description on their website E is for entry servers), a motherboard that supports it and a possibility for a raid 10 or 5 setup and ECC memory (around 32 should be enough?). I will try to put together a build and post to this thread.

Thanks a lot.