The potency of Mr. Nice seeds depends on the product you pick. If you are new to using medicinal marijuana, start out with something that is low potency. The goal should be to get results for your health needs with the least amount of the product. If that doesn't take care of the problem, you can bump up the amount you use.
Once you know your level of cannabis to use for relieve, you can plant accordingly. You can select the seeds that offer you the level of potency you want. You can also plant the number of them to give you the yield you need based on how much you use and how often you use the product. It can take some time to get your equations right so always go with more plants than you think you will need for your first couple of crops.
For the best results with Mr. Nice seeds, it is important to decide the results you want. Look for a product that will grow well in the conditions you can provide. This will reduce the chance of any of your plants not producing a large amount of cannabis for you to use for medicinal purposes.