I want to play games like GTA 5, CSGO and Minecraft sensibly on high graphics settings
The PC: intel core i5-9400 / 8gb Ram / 256gb SSD GTX 1650 4GB
I will certainly upgrade the PC with an additional HDD with 1 Tb. If possible also upgrade the RAM to 16GB.
Since GTA 5 is the most challenging game you've listed:
That's how it works. It may run a little worse with only 8GB of RAM, but otherwise you can expect that
For Minecraft safe
a friend of mine is playing on an imac 2009
How much fps worse? Approximately
It's hard to say. You can also watch it on YouTube. Depending on the situation, hardly or clearly (10-20% less power)
Resolution?
Do it yourself
Probably 20% less power where you live
Take a smaller SSD and a better graphics card / more ram
For mc and cs-go without problems!
gta is a bit more sophisticated but fairly well optimized so you will most likely never go above 60 fps…
Look at this. It's not a GTA, but in some games it's really a difference like day and night
Well, I doubt whether you can get high graphics settings. This is solely due to the weak graphics card. The only 4GB VRam are simply not enough in 2020. If you want to play on FullHD and want to set high settings, you should have at least one card with 6GB. And the performance of the 1650 is also very weak. If it were the super variant, it would look a little different.
This is because the Ram was almost fully utilized in the 1st, the games he called don't use as much memory, I had about 5fps more in gta with 16gb compared to 8gb, I also upgraded at that time