All autistic children are different, many children who do not have autism are speaking little at 2, including my own son who is now 3 and speaks well. Do you currently live in the UK? I notice English isn't your first language, and wonder if your son is being raised bi-lingual? If so, this could be a reason for behind average language development.
With 'severe' autism or level 3 autism, diagnosable as young as 2, I would expect to see obvious 'stims' things such as hand flapping or repetitive rocking when excited or stressed. Tiptoe walking, unusual eye movements-such as looking out corners of eyes, spinning themselves or toys, head banging, poor eye contact, lack of interest in other people, poor emotional regulation, poor sleep. All of these are just examples and not a check list.
Milder autism symptoms such as a general speech delay and occasional toe walking/ lining up/spinning of toys etc could just be a typical toddler which is why it tends to only be severe autism that is diagnosed at 2.
There are many reasons for poor speech at 2, such as glue ear, other hearing problems, or just a late talker.