8gb ram ddr3: 8Gb seems good, although in 2020 ddr3 is not acceptable for me. No, the performance will almost be the same but why not go for ddr4?
Ga H81M s2pv : I would want to go full ATX rather than mini. With mini you wont be able to install some coolers that are to big (I also had a mini and later I was able to afford a full ATX and meanwhile I couldnt mount this cooler which was great:
https://www.amazon.de/CSB-Thermalright-Macho-Sockel-306350/dp/B07WBYJDKL/ref=sr_1_2?__mk_de_DE=ÅMÅŽÕÑ&keywords=thermalright+macho+x2&qid=1585747485&sr=8-2 )
Psu :500 watt: more than enough
Gpu :1650 super 4gb ddr6: 6Gb of VRAM and then it would be gold but the graphics card is decent enough for 2020
1tb hdd: standard good choice. Personally I went 2TB bur for specific reasons and I could just afford it.
256gb ssd: Also a good choice. You could go go 125Gb or so but I think when it comes to boot ssd it's a must for 250Gb. However I highly recommend you get one from Samsung.
I3 4150 ,3.5 ghz(can upgrade to i7 4th gen): Now this is a bit tricky. Me, an individual, I have a personal thumb of rule when it comes to building a PC. I only go for parts that are considered good for me and do not pay attention to my budget. If I dont have enough money for a component I wish for then I save money instead of making compromises. I do not know what's your situation but I always want a CPU with at least 5.th generation in it (example: i3 5000 or i5 5000). Again when it comes to building PCs I always judge with stomach and not by statistics including game FPS and benchmarks.
Mind if I ask which cooler you are going to use?