Asperger was milder than autism.
Usually, yes. The main difference under the DSM IV was that no matter what your actual functioning level, those with a significant speech delay would receive a diagnosis of Autism, but those with no speech delay would receive a diagnosis of Asperger's.
This meant in practice that a person with Asperger's might be quite severely affected, have a lot of issues with communication, need a lot of support, not be able to find a job or a relationship, have difficulties at school and not gain qualifications. I have a family member who is like that, he is an adult and although he lives alone he needs a lot of support. There was also another member here a while back who was in a similar position (he got banned) and I think had his father acting as guardian. And yet he was diagnosed with Asperger's, not autism.
There also used to be HFA - high functioning autism. People with this were often very similar to those with Asperger's, except they had a speech delay as kids. Temple Grandin is an example of this.
Now, under the DSM 5, one's level is assessed according to how much support you need. So my family member, and the other member here that I mentioned above, would most likely receive a diagnosis of ASD2, that person who was in assisted living and had a guardian is probably closer to ASD3.
Of course, comorbids play a big role in this. People with ASD2 and 3 usually have comorbid diagnoses such as dyspraxia, dyscalculia, anxiety disorders, depression, dyslexia. Those with ASD3 often have severe developmental delays. Comorbids can have a way of exacerbating the ASD, meaning that they find it harder to cope and have greater difficulties in social communication and executive functioning.
I was diagnosed with moderate Asperger's, which I guess means that at the time, I required a moderate level of support. I don't know whether that means ASD1 or 2, but since, at the time, I wasn't coping and needed a lot of support, it might have been ASD2. If I were to be assessed now, I would more likely ben diagnosed with ASD1 because I no longer need so much support. Or, they might look at my life history, and decide on ASD2, I really don't know. It's entirely subjective.
I've noticed, having been on ASD forums like this one for a while, that quite a few older adults who are diagnosed in adulthood, receive an ASD2 diagnosis. I think that this is because although they may have coping/masking skills, they still struggle to cope more, burn out and crash and are more likely to have other issues such as anxiety or depression. They then get a diagnosis after seeking help. Those older adults who are ASD1 may come across as quirky or odd, have some anxiety issues but otherwise generally cope so although they may be aware of being on the spectrum, but don't necesarily seek help and may not be diagnosed. Of course, these are general tendencies, each case is different.