The low resistance ones are 2.2 ohm coils and the high ones are 3.2 ohm coils. Going to take more electricity to drive the high resistance and probably lower amount of vapor.
Maybe a mental error on your part, but this statement is simply not true. Lower resistance coils drain more amps (current) from the battery than does higher resistance coils. This is why sub-ohm coils (very low resistance) require a high wattage mod and/or high amp batteries.
...he was at 6 packs, no joke! Now he's down to 1 or 1 and a half. Sometimes up to 3 if he's really stressed but most of the time it's much better... So I'm thinking this would be a great in between. I just don't want it to be too expensive. I do want it to be worth it to him. He does want to quit but he's not "there" yet.
As a beginner, a "closed" system will be easier and more convenient for your dad, although he will pay more for that convenience in the long run. Pre-filled e-liquid cartridges and their proprietary gear are more expensive than "open" systems where you can use a variety of of e-juices and vape gear of your own choosing. Closed systems routinely use a higher nic content in the e-liquid, which better suits a beginner trying to make the switch from smoking.
The point that I'm trying to make here is: What would be the best introduction to vaping to get your father to make the switch? A closed system (cigalikes or a pod system) will be simpler in the beginning, if more expensive for the long run. Once he does quit smoking, learns that vaping is successful and worthwile, he can do his own research to find a more efficient, less expensive setup for the long term.
Perhaps one of the "Pod" systems would be a better fit for your dad:
Closed Systems like cigalikes and most pod systems are beginner-friendly, but generally do not allow you to add your own e-liquid. Your e-liquid flavor choices will be limited to the select few that the manufacturer offers. Gear choices will be limited to that one manufacturer's offerings, too.
Open Systems like the Ego battery devices and the more advanced "mods" are not quite as beginner user-friendly, but do allow you to use any e-liquid flavor offered by hundreds of e-liquid manufacturers. There is a much wider selection of battery devices and juice delivery attachments (tanks). This category is less expensive over the long run.
Vaping can be as easy or as difficult as you make it. The choices can be overwhelming, but knowledge gained from research can help narrow the choices. There literally is a great setup for nearly any type of person who is determined to make the switch.
I recommend you and your father read the below blogs to help make the decision:
Good Starter Setups for a Beginner Vaper
- Typical starter setups recommended for a new vaper.
Advancing Up the Vaping Ladder
- From cigalike batteries, to eGo's, to mods. Another picture dictionary of terminology and form factors for beginning vapers.
Proper Terminology: Is it a carto, a tank, or what? A Guide to Juice Delivery Devices
- A picture dictionary for beginners with descriptions of clearomizers, nano's, drip atomizers, bottom feeding mods, cartomizers, cartotanks, and RBA's (rebuildable atomizers). Includes video demos/reviews of all devices.