Hi and welcome,
Subjective means you feel weak, but there is no loss of strength, objective means there is a loss of strength that can be noted during a physical exam....
IF i understand you correctly, you are saying even though you feel weakness in your left leg and right arm, your neurological clinical signs were 'not' abnormal hence why the weakness is 'subjective'......add to your picture the addition of also having normal brain and spinal MRI's, your actually saying you don't have any diagnostic evidence that would be suggestive or consistent with your symptoms being caused by a neurological condition.
When diagnostic evidence is pointing away from neurological causation, then realistically the non neurological alternative medical explanations become a lot higher on the list of potential explanations....
Q: Is it typical to have weakness in right arm and left leg?
A: In MS it's not typical for the symptom of weakness to be subjective, MS symptoms are caused by brain and or spinal cord lesions which typically leave behind abnormal and measurable clinical signs (objective).
MS would typically present with neurological symptoms down one side of the body......what you are experiencing whilst being subjective, is also on the left and right sides of the body, one upper and one lower limb on opposite sides of the body isn't typical of neurological conditions as far as i understand, because that symptom pattern wouldn't follow basic neural pathways.
i would suggest you consult you family doctor and ask if there isn't the evidence of a neurological abnormality, what else could it be?
Keep in mind that if you are experiencing high levels of anxiety, mental health is a legitimate causation of subjective symptoms, one possible causation you may need to get ruled in or out too, it might be worth considering getting a mental health assessment if you think it might be of benefit to you going through all this, btw it usually is beneficial to get additional support when the issue is medically unknown, so please don't dismiss getting a mental health assessment without considering the short and long term benefits to you....
Hope that helps......JJ