Can I improve a project after submitting it to a CS conference? How much can I improve a project after submitting it to an academic conference in CS?

Recently, I submitted my first conference paper. The work is honest, but it was rushed due to getting promising results only a few days before the deadline. Furthermore, the process of trying to justify the work helped clarify it in my mind, and there are experiments, baselines, and comparisons I now believe I need to run to be more convincing. Is it standard to keep working on a project until the reviewers respond, such that I can say, "Thank you for such and such feedback. We are now including such and such an experiment/table/figure to address this concern." The writing could also be improved, but I'm not sure what is an acceptable number of modifications.
No one can stop you from becoming smarter ;-). 

In CS it is not uncoimmon, that you submit a first version of an algorithm / system etc., and improve it afterwards which might lead to the next publication. 

In your specific situation it might be a good idea to include the optimizations in the revision, as long as you do not change the overall algorithm / experiments etc which would invalidate the review process. Wording and grammar issues can always be corrected.

I would suggest to wait for the review, adress all reviewers comments, and maybe you can use your newer results / ideas to do so. 

Furthermore, you can always add additional information in your presentation. "In our paper we had the following results, but changing xyz led to even better results as shown here". Many people would consider making a new paper based on the optimized results, but without knowing your project it's hard to give advise whether it's a good idea or not (personally, I'm not a friend of incremental publishing).