I am actively looking for an ebike to be used by wife for touring. While I looked at hub wheel systems, I decided that a dedicated ebike with a mid-drive system is more functional, albeit, more expensive option, particularly for distance touring. I think the advantage of mid-drive system is that the bike functions more like a regular bike, without a throttle and regular bike wheels. I think one advantage of a hub kit is that you probably have more control over the battery capacity. Plus, if you like the bike you have, you can convert it. You could also consider using mid-drive conversion system.
In considering the range question, the big issue is battery capacity. A 400 wh lithium battery on a pedal assist (only works while you're pedaling, no throttle) should be good for about 35 to 50 real world miles depending on several factors including, the degree of assist used, the amount of climbing required, total weight of rider and gear, wind, etc. If you turn the assist off on the flats and only use it for climbs you could extend the range, perhaps significantly. You can always carry a spare battery with you to double your assisted range. It is my understanding that most batteries can be charged to about 80% in 90 minutes, with a full charge taking about an hour.
You might want to visit electricbikereviews.com, which is a very informative on ebikes, and issues regarding kits, dedicated ebikes, batteries, etc.