Are 4gb ram enough for minecraft?
If you do not use mods enough even 1gb. If you have the Java version, Minecraft rarely needs more than half a GB…
Very thin. It is also important that you have NO Intel iGPU.
Which notebook should it be?
Very borderline. I would take 8 then it is sure that you have fun playing.
Can I also upgrade? With 64 bit
With a laptop, you can't upgrade the RAM