The Roadster has a unique connector for charging with. Technically the charger is in the car and the part you plug into the wall is a connector but everyone will know what you mean by calling it a charger. Anyhow, the roadster was built before the industry standard J1772 connector, and also the Tesla connector found on the S/X/3. So some kind genus designed some adaptors to be able to use the J1772 and Tesla connectors. The J1772 is the CAN Jr and the Tesla being the CAN Sr. Both essential for travelling and charging from anywhere other than your own home. Many use the Tesla HPWC and a Tesla connector for daily use. There are benefits of Slow and faster charging. The slow charge will allow the cells to balance for a longer period of time, produce less heat and keep the pack stable. 110/120V however does not allow the car to utilize the HVAC to cool the pack down and nor does it need to because the the charge rate is fairly slow, all charging has some inherent losses so this is possibly less desirable for efficiency reasons. The sweet spot seems to be 32-40 A 220-240V allowing you HVAC, lower losses from cooling the pack and generally the most efficient cost/charge times.
The Roadster enjoys longer than expected pack life due to the fact the standard charge does not charge the pack fully, to take the pack to max usable capacity (around 95%) full you need to manually change the setting on the charge screen to 'RANGE' This will charge the pack to a higher capacity at the cost of reducing the pack life, over the course of the life of the pack this could be significant. The exception to this is using the initial 30 minutes of range charge to cool the pack as it automatically starts active cooling in this mode.
CAC is basically the best guess the car can make about the condition of the pack. The pack is only as good as the weakest brick. The data to brick level is found in the logs. The information for pulling the logs and using the program to read the logs are not for the faint hearted. There are some excellent threads already covering this.
Battery health: What is the ideal CAC ?
Help with vehicle logs
As mentioned if the company are not helpful maybe look elsewhere, there are some forum members here who IMO have outstanding cars at the same price point.
There a lot of informationI have glanced over but to point you in the right direction and for some dirty numbers, ideal range charge for most of us is around 210-230 and standard 170-180km for a healthy pack. Again this is a guess made by the car so number can and do move. Use ideal not the other number as some spirited driving can throw the numbers off wildly. generally 120V charging will also show a higher end charge of around 5-10% so be wary of very high numbers. Ask as many questions from the dealer and on the forum because many people have different view points and experiences that can give you information into as much detail as you are able to understand, however that sometimes confuses the issue also. Best of luck with the search and purchase.