I've done several Caninos in Spain and slept outside a lot. I've also met many people who only camped the whole way and had neither troubles or regrets. We all enjoyed it and had nice and comfortable nights...
Like said, there are not so many camping grounds. However, it's legally ok to wild-camp: there are just some rules to be aware of. I also disagree with the idea that the Camino is not suited for camping: it's a place like any other. It's always possible to find a decent and respectful spot to (wild-)camp; I found it not too hard to find such spots either.
As for gears, it's quite a matter... lots to say and think about it! But it's doable to have stuffs that are not too heavy or too expensive. (Ie. I've walked a Camino with a 6kg backpack that had everything I needed to comfortably sleep and cook outside).
Wild camping is very regulated in Spain and reference to bivouacking is vague. The topic is quite complex and gives Spanish people themselves quite a headache. A state law considers camping a gathering of tents in a 500m radius. It's "wild camping" when out of camping grounds and forbidden for more than 3 tents, 10 campers and 3 days in a row. So, legally and theoretically, bivouacking is ok. But each autonomous community can regulate their own area to their will and sames goes for municipalities: that's where things get messy.
To make it short and simple, on the CFrancés (Navarra, La Rioja, Castilla y Leon and Galicia), if it's camping as 1 tent, 1 person, 1 night, it's legally and theoretically ok.
Note also that legally, one is supposed to respect the environment (basically, leave no trace), keep some distance with drinkable water and monuments, that camp fire are a touchy subject and that some areas are more regulated than others (natural parks, beaches...)
Of course, all of this doesn't necessarily keep you from eventual troubles or visits by the Guardia Civil in the middle of the night...
All that said, at the end, it's down to personal needs, preferences and choices. Like you say, there are lots of mixed information: seeking advice is good, but you'll have mixed ones too. The idea is to narrow the answers to find your own and unique truth. I think it's all about knowing yourself and answering questions...
Why do you want to camp? Is is for the fun/beauty/challenge/... of it, or to save money? How adventurous are you? What degree of (dis-)comfort can you stand? Are you ok to sleep in open spaces or do you need secured ones? Do you need a tent? Could you be happy with a tarp? ... And so on
Buen prep!