If you're low on something, game will throw it at you with scans or covert op bonus - so maxing out your supplies increases chance you'll get a +1 available - this is how you can get to 16 contacts with just one avenger room used on that You big monthly supplies and get continent bonuses this way. Like there is one where you can only send a team of three and another where your highest ranking soldier allowed is sgt.ДЇill them. Although some are really helpful, some are quite problematic. Oh and in WotC, guerilla ops sometimes have sitereps. As for the type of mission, this doesn't really matter, but a hack mission has a chance of a hack reward whereas a destroy the relay type mission does not. Some people don't like the dark event show of force, although I see it as just extra XP. Personally, I prioritize the reward (for example, early I prefer engineers & scientists over intel or supplies), but there are a few dark events (like alien cypher that doubles intel costs) that are pretty painful so I will take them into account. They'll typically be three different kinds of missions with three different rewards and three different dark events that they counter.

OP, guerilla ops come in packs of three and you get to select one of them. Sometimes you'll only have one or two to pick from instead of all three. Well, you will miss out on some options for guerilla ops if you don't contact more regions.

Xcom 2 how to get more contacts