As for the start, sell your war and transport fleet to Burgundy(only they will accept) and use the moneys yo get(160?) to build trade ships. The traditions make those ships a medium fighting force and your key to a strong economy. Use them to protect trade in Lübeck.
Use the ally tactic mentioned over with Sweden and rivals of Denmark. NEVER try to ally France(did it many times and failed hard) before your fleet is almost as strong as the english. Instead try to ally England and get them in a war with Sweden true the alliance they have with Scotland. If Scotland keep their borders England will never try to take you before it is to late for them. Take out Scotland when your fleet is stronger than the english and your army can compete with them and this is the time to ally France. If you decide to try France instead your fleet will die because Sweden often allies England and then you will have english troops landing in Agder and swedish coming from the east. Also Muscovy is a good ally to get. Also I would advice you to take Skåne and Halland(get claim if possible) in the independence war and hinder Sweden from occupying anything. Those provinces gives you trade power and more important, forcelimit. Use some more wars to take all the danish lands, but in the meantime you should also take from Sweden if possible, espesially Dalaskogen for money and Västergötland for land connection->no need for a big transport fleet. In every war with Sweden take out their fleet if possible. This can be very helpful if your army suffer. Bait the Se
As the game goes try to ally and diplovassalize northern minors in HRE. This can help a lot against coalitions and other problems you can get.
As for ideas group I would from the start of the game set focus to diplomacy and have diplomatic as the first, exspansion as the second and quantity as the third. The norwegian ideas are one of the best for colonisation with the colonist idea, plus you get lot more trade and ships with colonies so you must go as early as possible to get the best areas while Spain and Portugal are focusing on Africa and Brazil. Get to technology level 7(by this time you should have 2 or 1 colonist) in diplotech asap after getting the 3 first ideas in exploration and after that take ideas before tech in diplomatic. Exceptions would be levels where light ships are upgraded. When you have filled the 3 first idea groups always use the policies until there is nothing more to colonice. This will make the colonicing faster and Keep in mind if you want to go protestant or reformed it could be smart to wait with the fifth colony in each region before you have shifted to get a CN of your religion. Take coast, trade power and start with caribbean early to take the best for less. Money can be a problem early because you will have 5 colonist working and maybe are forced to fight wars at home.
Exploration is for colonising, naval FL and CB
Expansion is for colonist, trader and CB
Quantity is for getting a army big enough to compete and manpower. A small enough army can't compete no matter how good the quality is
Further on you should get :
Administrative for FL and cheap mercenaries. Even with quantity manpower will be a problem and by this time the money shall flow to Lübeck where you have the greatest fleet in the world and whole denmark which means the limit on mercenaries won't be money, but how many avaible.
Maritime for cheapest and strongest merchant fleet ever seen. With this you won't need big ships and can instead just hunt down all fleet with your 12ducat light ships with +30% combat ability. And no slow ships so it don't need to split to cover to much
Defensive/Quality/Quantity: Reasons for those are well known and only thing is that you should get two of those. Myself I would take defensive first and then one of the others
Influence: For not getting hated that much, to take colonies when the war goal is elsewhere without to much penalty and to get as much as possible from your subject(which will be many). Also liberty desire will be lower and more vassals and alliances are avaible(not right written?)
When at war, use the terrain. Norway is filled with it and always mind it when attacking or defending.
Further on luck is always a factor on how easy it will be, if your early rulers are good both in monarch point, but also in shock and siege it will be much easier to take on Sweden early on and you will crush Spain and Portugal in Amerika and the race there. Also the situation in Europe will "never" be the same twice and here your luck can play a big role.
And lastly. NEVER underestimate Sweden before they are dead. Even thou you have taken some land from them they will always grow bigger with ideas and they have cheap mercenaries and a high quality army.
This was the way I used to get the Norwegian wood achievement. I won't promise results every time, but it will help a lot.
EDIT: To answers your question, they are playable in a good way and very fun where you must use their strenghts and cover their weaknesses. This is only one way to do it so it can be very interesting to find other ways to do it, but still, Sweden is your main foe and this will happen every time.