Hi @Doudi many thanks for your response.
To answer your first question, yes the IC is infinitely scalable, with more subnets or larger subnets, but you have to consider the impact this has on performance (having more nodes in one subnet will require more nodes having to reach consensus, and having many subnets will mean an increase in cross-subnet communication).
This immediately points to your second question, in that there are several trade-offs to be made in terms of reaching the right balance between capacity and performance. I would suggest to have a look and the discussion being picked up in this forum thread, and please feel free to post any additional questions there as well. As is stated in this thread, in terms of load balancing and as a next step - abstracting this away in the protocol - this is something that the IC could grow towards but of course takes development time.
Hope this helps answer your question.