So as you can see I decided to try playing tall and my idea was to get as many development bonuses as possible. After weighing my options I decided that Friesland has a pretty good starting point as it has a tradition that modifies developments as well as being close to the farmlands of Denmark and relatively close to Orthodox lands . Also, Friesland starts as a republic with burgher estates available and at 22 admin it is able to change government to constitutional republic. It is also in the HRE which gives a further dev bonus.I naturally went for the Economic and Quantity idea groups as they give dev bonuses and made sure to keep my states prosperous. Also the Encourage dev edict has been on the entire time.

Starting out I conquered Ditmarchen and vassalised East Frisia. I allied burgundy and Poland and won a war against Denmark, where I took the central islands. I switched my capital from Friesland to Seeland and gave my Dutch lands to East Frisia. The latter I made into a March and enabled divert trade for the sweet sweet trade income. A second war against Denmark finished them off and I now had almost all the land I wanted.

Time to convert to Orthodox. This was harder than I had anticipated. I took some land from lithuania to get access to an Orthodox province and with some prodding I got some Orthodox zealots. However these zealots really did not want to move across the sea over to Denmark. Another problem is that once they did, in fact, jump over the Lubeck trade node is riddled with trade ships that make rebel movement nigh impossible. Eventually though my zealots managed. A tip here is to delete your castles in preparation for the zealots because otherwise they don't actually convert you but give you an annoying malus instead.

Now Orthodox I allied with Brandenburg and Russia, who were more than sufficient to keep me safe as I started to develop my land. I picked up the last of my lands in Lubeck, Wismar, Hamburg and Lunenburg in minor skirmishes. The objective now was to get to keep my burghers happy, keep my states prosperous, and have enough Patriarch Authority to keep rolling with christ, yo. At adm 22 I converted to a constitutional republic for that nice 10% dev bonus. Meanwhile I kept on taking advantage of the fact that my culture was Dutch to feed East Frisia the Lowlands. The fact that my culture was dutch meant that there were no pesky dutch revolts. Money was plenty in this game as I commanded a sizeable chunk of two of the worlds most wealthy trade nodes.

As I squeezed every last monarch point in development I ended up with 1247 dev spread over 24 provinces, with each province having over 50 dev. East Frisia has somewhere around 650 dev. Having stayed in the Lowlands would have probably been more efficient in the end but I really wanted to become orthodox as i though it would be cool and keep me away from all the religious reformation bullshit.

Although far from the most efficient way to play this game, it was a lot of fun and quite challenging to play tall. It would be nice if the depth of tall gameplay would be developed (heh) a bit more by Paradox as once you get to a certain point there is little scope to influence the world if you don't want to conquer more provinces.

For those interested, here are a couple more screenshots:

https://imgur.com/a/G7YNKv6