I understand that RAM required for optimization problem is problem specific and some problems require much more memory. I am thinking how much RAM I need for my system and need to decide between getting 32 GB or 64 GB. The processor has 24 threads which means using more threads will require more RAM. Is 32 GB RAM enough for most optimization problems of the form LP, MILP, QP and MIQP problems?
Easy answer: 64 GB
With 24 threads (is this already including hyperthreads? Maybe not, so we are actually talking about 48 threads...) you'll have about 2 and a half GB for every thread - that's not very much if you really want to make good use of those threads. So going for 32 GB is definitely the wrong move and you'll most likely regret this choice.
AFAIK, every competitive optimization solver treats memory as a more or less abundant resource and will often have no difficulties filling it up. You are more likely to use some parameter settings to avoid out-of-memory issues even with 64 GB, so if possible, you should go for even more memory.