7s and 8s spacing is the same so if you're comfortable shifting your 7s now, 8s will be the same. And since the wheel is already spaced around 8s you might as well go that route. Personally I'm not a fan of super wide cassettes, since the extra range comes at the expense of wider spacing in the middle gears where you do 95% of the riding.

I prefer to go the route of a triple crank when setting up wide range gearing for touring or just hilly areas. Combined with a medium range cassette (12-26 or 28) this gives excellent gear selection in the mid range, while allowing super low gears, usually lower than what can be achieved with a double and a 34t rear. If you do go the triple route, consider your needs at the high end. Most people have little use for the top end 53/11 or 53/12 or typical road bikes, so a triple built around a 50t or 48t outer chainring might give you combinations you'll actually ride.

If you decide to open up all possibilities, start by using a gear chart to calculate what gear ratio you do most of your level ground riding, what you want as a low, and what high gear you actually would use. Then find a cassette which combined with a granny will give you the low end needed. With that cassette in mind pick a chainring that will give you your level gear using the outer middle of the cassette (sweet spot), and the necessary high with the outermost. Lastly slot in a middle (if you have a choice) which gives you a good working low range off the middle and inner cassette sprocket for the rolling terrain (or when you begin to tire). I try to have the middle chainring gear values be a half interval off from the outer so rather than duplicate values, I can use either middle or outer rings with the middle of the cassette to create even finer spacing.